1 chapter 22 chemistry of the nonmetals ldescriptive chemistry of the elements is consistent with...

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Chapter 22Chemistry of The NonMetals

Chapter 22Chemistry of The NonMetals

Descriptive chemistry of the elements is Descriptive chemistry of the elements is consistent with the various principles consistent with the various principles discussed earlier.discussed earlier.

We will focus on trends in and explanations We will focus on trends in and explanations for the observed behavior of the elements.for the observed behavior of the elements.

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22.1 General Concepts: Periodic Trends

22.1 General Concepts: Periodic Trends

Main-group elements -- the valence Main-group elements -- the valence electrons are filling s and p orbitalselectrons are filling s and p orbitals

Three types of main-group elements: Three types of main-group elements: metal, metalloid, nonmetalmetal, metalloid, nonmetal

Increasing metallic character going down a Increasing metallic character going down a group and from right to left across a periodgroup and from right to left across a period

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Group WorkGroup Work

List the relative properties of the metals:List the relative properties of the metals:volatilityvolatilitymelting and boiling pointsmelting and boiling pointsdensitydensitythermal conductance thermal conductance electrical conductanceelectrical conductanceappearance as solidsappearance as solidsbrittlenessbrittlenesstypical structuretypical structurebondingbondingtendency to lose or gain electronstendency to lose or gain electronsacidity/basicity of oxidesacidity/basicity of oxides

non-volatilenon-volatilehighhighhighhighhighhighhighhighshiny/lustrousshiny/lustrousmalleablemalleableatomic crystalsatomic crystalsmetallicmetallicloselosebasicbasic

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List the relative properties of the non-metals:List the relative properties of the non-metals:volatilityvolatilitymelting and boiling pointsmelting and boiling pointsdensitydensitythermal conductance thermal conductance electrical conductanceelectrical conductanceappearance as solidsappearance as solidsbrittlenessbrittlenesstypical structuretypical structurebondingbondingtendency to lose or gain electronstendency to lose or gain electronsacidity/basicity of oxidesacidity/basicity of oxides

volatilevolatilelowlowlowlowlowlowlowlowdulldullsoft or brittlesoft or brittlediscrete moleculesdiscrete moleculescovalentcovalentgaingainacidicacidic


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MetalloidsMetalloids

Metalloids: physical properties more like Metalloids: physical properties more like those of metals, but chemical reactivity is those of metals, but chemical reactivity is more like that of nonmetals; many atomic more like that of nonmetals; many atomic properties are intermediate between those properties are intermediate between those of metals and of nonmetalsof metals and of nonmetals

SiSi

AsAs

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Period 2 Elements are UniquePeriod 2 Elements are Unique

Compounds formed between nonmetals Compounds formed between nonmetals tend to be molecular.tend to be molecular.

As we move down the periodic table As we move down the periodic table bonding changes.bonding changes.

The third period onwards has accessible The third period onwards has accessible dd--orbitals that can participate in bonding.orbitals that can participate in bonding.

Therefore, the octet rule can be broken for Therefore, the octet rule can be broken for the third period onwards.the third period onwards.

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Period 2 ElementsPeriod 2 Elements

The first member of a group The first member of a group can form can form bonds more bonds more readily than subsequent readily than subsequent members.members.

Si is much larger than C and Si is much larger than C and the 3the 3pp orbital is much larger orbital is much larger than the 2than the 2pp orbital, so the orbital, so the overlap between 3overlap between 3pp orbitals to orbitals to form a form a 33pp bond is significantly bond is significantly poorer than for a poorer than for a 22pp bond. bond.

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Period 2 ElementsPeriod 2 Elements

Since the Si-Si Since the Si-Si bond is bond is much weaker than the C-C much weaker than the C-C bond, Si tends to form bond, Si tends to form bonds.bonds.

SiOSiO22 is a network solid with is a network solid with Si-O bonds.Si-O bonds.

COCO22 is a gas with O=C=O is a gas with O=C=O bonds.bonds.

1010

Lightest Elements are UniqueLightest Elements are Unique

Properties of the first element in each group Properties of the first element in each group are usually more distinctive, while the rest are usually more distinctive, while the rest of the elements in a group have similar of the elements in a group have similar propertiesproperties

The unusual properties of the first element The unusual properties of the first element in a group can be explained on the basis of in a group can be explained on the basis of its its unusually small size, which arises unusually small size, which arises because the valence electrons are not because the valence electrons are not shielded from the nucleusshielded from the nucleus and the electrons and the electrons are held relatively tightly in the atomare held relatively tightly in the atom

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Trends in Properties of the Elements

Trends in Properties of the Elements

1212

22.2 Hydrogen22.2 Hydrogen

Isotopes of HydrogenIsotopes of HydrogenThere are three isotopes of There are three isotopes of

hydrogen: Protium hydrogen: Protium 1111H, deuterium H, deuterium

2211H, and tritium H, and tritium 33

11H.H.

Deuterium (D) is about 0.0156 % of Deuterium (D) is about 0.0156 % of naturally occurring H.naturally occurring H.

Tritium (T) is radioactive with a Tritium (T) is radioactive with a half-life of 12.3 yr.half-life of 12.3 yr.

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Properties of HydrogenProperties of HydrogenProperties of HydrogenProperties of Hydrogen

Hydrogen is unique.Hydrogen is unique.Hydrogen has a 1Hydrogen has a 1ss11 electron configuration so it electron configuration so it

is placed above Li in the periodic table.is placed above Li in the periodic table.However, H is significantly less reactive than However, H is significantly less reactive than

the alkali metals.the alkali metals.Hydrogen can gain an electron to form HHydrogen can gain an electron to form H--, ,

which has a He electron configuration. which has a He electron configuration. Therefore, H could be placed above the Therefore, H could be placed above the halogens.halogens.

However, the electron affinity of H is lower However, the electron affinity of H is lower than any halogen.than any halogen.

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Properties of HydrogenProperties of HydrogenProperties of HydrogenProperties of Hydrogen

Elemental hydrogen is a colorless, odorless gas at Elemental hydrogen is a colorless, odorless gas at room temperature.room temperature.

Since HSince H22 is nonpolar and only has two electrons, is nonpolar and only has two electrons,

the intermolecular forces are weak (boiling point -the intermolecular forces are weak (boiling point -253253C, melting point -259C, melting point -259C). What kind of C). What kind of intermolecular forces?intermolecular forces?

The H-H bond enthalpy is high (436 kJ/mol). The H-H bond enthalpy is high (436 kJ/mol). Therefore, reactions with hydrogen are slow and a Therefore, reactions with hydrogen are slow and a catalyst needs to be used.catalyst needs to be used.

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Properties of HydrogenProperties of Hydrogen

When hydrogen reacts with air, explosions When hydrogen reacts with air, explosions result (result (HindenburgHindenburg exploded in 1937): exploded in 1937):

2H2H22((gg) + O) + O22((gg) ) 2H 2H22O(O(ll)) HH = -571.7 kJ = -571.7 kJ

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Preparation of HydrogenPreparation of HydrogenPreparation of HydrogenPreparation of Hydrogen

In the laboratory hydrogen is usually In the laboratory hydrogen is usually prepared by reduction of an acid.prepared by reduction of an acid.

Zn is added to an acidic solution and Zn is added to an acidic solution and hydrogen bubbles are formed.hydrogen bubbles are formed.

The hydrogen bubbles out of solution The hydrogen bubbles out of solution and is collected in a flask.and is collected in a flask.

The collection flask is usually filled The collection flask is usually filled with water so the volume of hydrogen with water so the volume of hydrogen collected is the volume of water collected is the volume of water displaced.displaced.

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Preparation of HydrogenPreparation of HydrogenPreparation of HydrogenPreparation of Hydrogen

What other metals could be used to prepare What other metals could be used to prepare hydrogen by reaction with acid? What hydrogen by reaction with acid? What property would we examine?property would we examine?

In larger quantities, hydrogen can be In larger quantities, hydrogen can be prepared by the reduction of methane in prepared by the reduction of methane in the presence of steam at 1100the presence of steam at 1100C:C:

CHCH44((gg) + H) + H22O(O(gg) ) CO( CO(gg) + 3H) + 3H22((gg))

CO(CO(gg) + H) + H22O(O(gg) ) CO CO22((gg) + H) + H22((gg))

1818

Uses of HydrogenUses of HydrogenUses of HydrogenUses of Hydrogen

Hydrogen is used for ammonia production Hydrogen is used for ammonia production and to hydrogenate vegetable oils to make and to hydrogenate vegetable oils to make margarine and shortening.margarine and shortening.

Hydrogen is used to manufacture methanol:Hydrogen is used to manufacture methanol:

CO(CO(gg) + 2H) + 2H22((gg) ) CH CH33OH(OH(gg))Hydrogen is being considered for direct use Hydrogen is being considered for direct use

as a fuel in automobiles. Would we want to as a fuel in automobiles. Would we want to carry around tanks of hydrogen? How else carry around tanks of hydrogen? How else could we store it?could we store it?

1919

Binary Hydrogen CompoundsBinary Hydrogen CompoundsBinary Hydrogen CompoundsBinary Hydrogen Compounds

Three types of binary hydrogen compounds are Three types of binary hydrogen compounds are formed:formed: ionic hydrides (e.g. LiH, made between metals and H);ionic hydrides (e.g. LiH, made between metals and H); metallic hydrides (e.g. TiHmetallic hydrides (e.g. TiH22, made between transition , made between transition

metals and H); andmetals and H); and molecular hydrides (e.g. CHmolecular hydrides (e.g. CH44, made between nonmetals , made between nonmetals

and metalloids and H). and metalloids and H).

Thermal stability (measured by Thermal stability (measured by GGff) decreases as ) decreases as

we go down a group and increases across a period.we go down a group and increases across a period.

2020

Binary Hydrogen CompoundsBinary Hydrogen Compounds

Most stable is HF.Most stable is HF.Metal hydrides, Metal hydrides,

such as CaHsuch as CaH22, ,

react with water react with water to give Hto give H22 and and

metal hydroxide.metal hydroxide.

GGff

2121

22.5 Oxygen22.5 Oxygen

Properties of OxygenProperties of OxygenOxygen has two allotropes: OOxygen has two allotropes: O22 and O and O33..OO22 is a colorless, odorless gas at room is a colorless, odorless gas at room

temperature.temperature.The electron configuration is [He]2The electron configuration is [He]2ss2222pp44, ,

which means the dominant oxidation state which means the dominant oxidation state is 2-.is 2-.

The O=O bond is strong (bond enthalpy 495 The O=O bond is strong (bond enthalpy 495 kJ/mol).kJ/mol).

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Preparation of OxygenPreparation of OxygenPreparation of OxygenPreparation of Oxygen

Commercially: obtained by fractional distillation Commercially: obtained by fractional distillation of air. (Normal boiling point of Oof air. (Normal boiling point of O22 is -183 is -183C and C and

NN22 -196 -196C.)C.)

Laboratory preparation of oxygen is the catalytic Laboratory preparation of oxygen is the catalytic decomposition of KClOdecomposition of KClO33 in the presence of MnO in the presence of MnO22::

2KClO2KClO33((ss) ) 2KCl( 2KCl(ss) + 3O) + 3O22((gg).).

Atmospheric oxygen is replenished by Atmospheric oxygen is replenished by photosynthesis (process in plants where COphotosynthesis (process in plants where CO22 is is

converted to Oconverted to O22 in the presence of sunlight). in the presence of sunlight).

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Uses of OxygenUses of Oxygen

Most widely used as an oxidizing agent. Most widely used as an oxidizing agent. (e.g. in the steel industry to remove (e.g. in the steel industry to remove impurities.)impurities.)

Oxygen is used in medicine.Oxygen is used in medicine. It is used with acetylene, CIt is used with acetylene, C22HH22 for for

oxyacetylene welding:oxyacetylene welding:

2C2C22HH22((gg) + 5O) + 5O22((gg) ) 4CO 4CO22((gg) + ) +

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OzoneOzone

Pale blue, poisonous gas.Pale blue, poisonous gas.Ozone dissociates to form oxygen:Ozone dissociates to form oxygen:

OO33((gg) ) O O22((gg) + O() + O(gg)) HH = 107 kJ = 107 kJOzone is a stronger oxidizing agent than Ozone is a stronger oxidizing agent than

oxygen:oxygen:

OO33((gg) + 2H) + 2H++((aqaq) + 2e) + 2e-- O O22((gg) + H) + H22O(O(ll) ) EE = 2.07 V = 2.07 V

OO22((gg) + 4H) + 4H++((aqaq) + 4e) + 4e-- 2H 2H22O(O(ll) ) EE = 1.23 V = 1.23 V

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OzoneOzone

Ozone can be made by passing an electric Ozone can be made by passing an electric current through dry Ocurrent through dry O22::

3O3O22((gg) ) 2O 2O33((gg))

2626

Peroxides and SuperoxidesPeroxides and SuperoxidesPeroxides and SuperoxidesPeroxides and Superoxides

Peroxides: have an O-O bond and O in the Peroxides: have an O-O bond and O in the -1 oxidation state.-1 oxidation state.Hydrogen peroxide is unstable and Hydrogen peroxide is unstable and

decomposes into water and oxygen:decomposes into water and oxygen:

2H2H22OO22((ll) ) 2H 2H22O(O(ll) + O) + O22((gg), ), HH = -196.0 kJ = -196.0 kJ

The oxygen produced will kill bacteria.The oxygen produced will kill bacteria.

Peroxides are important in biochemistry: Peroxides are important in biochemistry: it is produced when Oit is produced when O22 is metabolized. is metabolized.

2727

PeroxidesPeroxides

Disproportionation occurs when an element Disproportionation occurs when an element is simultaneous oxidized and reduced:is simultaneous oxidized and reduced:

2H2H++((aqaq) + H) + H22OO22((aqaq) + 2e) + 2e-- 2H 2H22O(O(ll))

EE = 1.78 V = 1.78 V

OO22((gg) + 2H) + 2H++((aqaq) + 2e) + 2e-- H H22OO22((aqaq))

EE = 0.68 V = 0.68 VDisproportionation: Disproportionation:

2H2H22OO22((aqaq) ) 2H 2H22O(O(ll) + O) + O22((gg) ) EE = 1.10 V = 1.10 V

2828

SuperoxidesSuperoxides

Superoxides: have an O-O Superoxides: have an O-O bond and O in an oxidation bond and O in an oxidation state of -½ (superoxide ion is state of -½ (superoxide ion is OO22

--).).Usually form with active Usually form with active

metals (KOmetals (KO22, RbO, RbO22 and CsO and CsO22).).Potassium superoxide reacts Potassium superoxide reacts

with water vapor from the with water vapor from the breath to form oxygen gas.breath to form oxygen gas.4KO4KO22 + 2H + 2H22O O 3O 3O22 + 4KOH + 4KOH

2929

22.3 The Noble Gases22.3 The Noble Gases

Noble Gas CompoundsNoble Gas Compounds Noble gases are very unreactive.Noble gases are very unreactive. All elements have high ionization energies.All elements have high ionization energies. He is the most important noble gas as liquid He is the most important noble gas as liquid

helium is used as a coolant.helium is used as a coolant. The heavier noble gases react more readily than The heavier noble gases react more readily than

the lighter ones.the lighter ones. The most common compounds of noble gases are The most common compounds of noble gases are

xenon fluorides.xenon fluorides. Xenon fluorides have Xe in the +2 to +8 oxidation Xenon fluorides have Xe in the +2 to +8 oxidation

states.states.

3030

Noble Gas CompoundsNoble Gas Compounds

Noble gas Noble gas compounds violate compounds violate the octet rule.the octet rule.

3131

Noble Gas CompoundsNoble Gas Compounds

In the presence of water, xenon fluorides In the presence of water, xenon fluorides form oxyfluorides:form oxyfluorides:

XeFXeF66((ss) + H) + H22O(O(ll) ) XeOF XeOF44((ll) + 2HF) + 2HF

XeFXeF66((ss) + 3H) + 3H22O(O(ll) ) XeO XeO33((aqaq) + 6HF) + 6HF

The only other noble gas compound known The only other noble gas compound known is KrFis KrF22, which decomposes at -10, which decomposes at -10C.C.

Xenon fluorides are more stable than the Xenon fluorides are more stable than the oxides and oxyfluorides.oxides and oxyfluorides.

3232

22.4 Group 7A: The Halogens22.4 Group 7A: The Halogens

F, Cl, Br, I, AtF, Cl, Br, I, AtMost common are chlorine, bromine, and Most common are chlorine, bromine, and

iodineiodine

Fluorine has properties atypical of the groupFluorine has properties atypical of the groupAstatine is radioactive and exists naturally Astatine is radioactive and exists naturally

only in very small amountsonly in very small amounts

3333

HalogensHalogens

The halogens exist as diatomic moleculesThe halogens exist as diatomic moleculesAt room temperature, fluorine is a yellow At room temperature, fluorine is a yellow

gas, chlorine is a pale green gas, bromine is gas, chlorine is a pale green gas, bromine is a red liquid, and iodine is a purple solida red liquid, and iodine is a purple solid

The elements have very high ionization The elements have very high ionization energies, typical of nonmetalsenergies, typical of nonmetals

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Properties of the HalogensProperties of the Halogens

Outer electron configurations: Outer electron configurations: nsns22npnp55..All halogens have large electron affinities.All halogens have large electron affinities.Most common oxidation state is -1, but Most common oxidation state is -1, but

oxidation states of +1, +3, +5 and +7 are oxidation states of +1, +3, +5 and +7 are possible.possible.

Halogens are good oxidizing agents.Halogens are good oxidizing agents.Each halogen is the most electronegative Each halogen is the most electronegative

element in its row.element in its row.

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Properties of the HalogensProperties of the Halogens

The properties of the halogens vary The properties of the halogens vary regularly with their atomic number.regularly with their atomic number.

3636

FluorineFluorine

The bond enthalpy of FThe bond enthalpy of F22 is low. Hence fluorine is low. Hence fluorine is very reactive.is very reactive.

Water is oxidized more readily than fluoride, Water is oxidized more readily than fluoride, so Fso F22 cannot be prepared by electrolysis of a cannot be prepared by electrolysis of a salt solution. Fsalt solution. F22 is an extremely reactive gas, is an extremely reactive gas, which reacts with all the elements, except which reacts with all the elements, except oxygen and the lighter noble gases, to form oxygen and the lighter noble gases, to form stable fluorides, often explosively.stable fluorides, often explosively.

FF22 is such a strong oxidizing agent that it can is such a strong oxidizing agent that it can convert oxides, including water, to molecular convert oxides, including water, to molecular oxygenoxygen

3838

ChlorineChlorine

Chlorine exists as chlorides in sea water, Chlorine exists as chlorides in sea water, salt lakes, and brine depositssalt lakes, and brine deposits

ClCl22 gas prepared industrially by the gas prepared industrially by the

electrolysis of sodium chloride solutionselectrolysis of sodium chloride solutionsAlso a by-product of the preparation of Also a by-product of the preparation of

metals by electrolysis of molten salts such as metals by electrolysis of molten salts such as NaCl, MgClNaCl, MgCl22, and CaCl, and CaCl22

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ChlorineChlorine

Most ClMost Cl22 is used as a raw material in the is used as a raw material in the

production of other chemicals, in the production of other chemicals, in the synthesis of herbicides and insecticides, in synthesis of herbicides and insecticides, in the bleaching of textiles and paper, in the bleaching of textiles and paper, in purifying drinking water, and in the purifying drinking water, and in the production of plastics such as polyvinyl production of plastics such as polyvinyl chloride (PVC)chloride (PVC)

4040

BromineBromine

Bromine exists in small quantities in the Bromine exists in small quantities in the form of bromides co-existing with chloridesform of bromides co-existing with chlorides

Prepared by reacting a solution containing Prepared by reacting a solution containing bromide ion with chlorinebromide ion with chlorine

4141

BromineBromine

Uses of bromine:Uses of bromine:as a bleach as a bleach in the manufacture of bromide in the manufacture of bromide

compoundscompoundsethylene bromide, Cethylene bromide, C22HH44BrBr22, used as an , used as an

antiknock agent in gasoline antiknock agent in gasoline

4242

IodineIodine

Iodine exists as iodides in brines and Iodine exists as iodides in brines and seaweed, and as iodates in deposits of seaweed, and as iodates in deposits of sodium nitrate (NaNOsodium nitrate (NaNO33, also called Chile , also called Chile

saltpeter)saltpeter)Recovered by oxidation of IRecovered by oxidation of I-- with Cl with Cl22 or by or by

reduction of IOreduction of IO33-- with HSO with HSO33

--

Used as an antiseptic and disinfectant and Used as an antiseptic and disinfectant and as a reagent for chemical analysisas a reagent for chemical analysis

4343

AstatineAstatine

Not much is known about its chemistryNot much is known about its chemistry It is highly radioactive; all chemical studies It is highly radioactive; all chemical studies

have used small quantities added to iodine have used small quantities added to iodine solutions and measure behavior by solutions and measure behavior by determining where the radioactivity ends determining where the radioactivity ends up.up.

The total amount in the Earth’s crust is The total amount in the Earth’s crust is estimated to be < 30 g at any one time.estimated to be < 30 g at any one time.

4444

HalogensHalogens

In addition to the common -1 and 0 In addition to the common -1 and 0 oxidation numbers, the halogens (except for oxidation numbers, the halogens (except for fluorine) exist with each positive oxidation fluorine) exist with each positive oxidation number through +7number through +7

Halogen oxides are known with oxidation Halogen oxides are known with oxidation numbers as high as +7; most are very numbers as high as +7; most are very strong oxidizing agentsstrong oxidizing agents

06m02vd1.mov06m02vd1.movGummy bears + KClOGummy bears + KClO33

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Oxyacids and OxyanionsOxyacids and OxyanionsOxyacids and OxyanionsOxyacids and Oxyanions

Fluorine only forms one oxyacid: HOF. Fluorine only forms one oxyacid: HOF. Oxygen is in the zero oxidation state.Oxygen is in the zero oxidation state.

All are strong oxidizing agents.All are strong oxidizing agents.All are unstable and decompose readily.All are unstable and decompose readily.Oxyanions are more stable than Oxyanions are more stable than

oxyacids. oxyacids. Acid strength increases as the oxidation Acid strength increases as the oxidation

state of the halogen increases.state of the halogen increases.

4646

Periodic AcidPeriodic Acid

Periodic (HIOPeriodic (HIO44) and paraperiodic (H) and paraperiodic (H55IOIO66) )

acid have iodine in the +7 oxidation state.acid have iodine in the +7 oxidation state.Periodic acid is a strong acid, paraperiodic Periodic acid is a strong acid, paraperiodic

acid is a weak acid (Kacid is a weak acid (Ka1a1 = 2.8 = 2.8 10 10-2-2, K, Ka2a2 = =

4.9 4.9 10 10-9-9).).The large iodine atom allows 6 oxygen The large iodine atom allows 6 oxygen

atoms around it.atoms around it.Smaller halogens cannot form this type of Smaller halogens cannot form this type of

compound.compound.

4747

Strength of OxoacidsStrength of Oxoacids

4949

22.6 The Other Group 6A Elements: S, Se, Te, and Po (Chalcogens)

22.6 The Other Group 6A Elements: S, Se, Te, and Po (Chalcogens)

Trend that affects other properties is the Trend that affects other properties is the increase in metallic character down the increase in metallic character down the group, indicated by the decreases in group, indicated by the decreases in ionization energy and electronegativityionization energy and electronegativity

OO22

SS88

Se

TeTe

5050

Group 6AGroup 6A

Nonmetallic character dominates in this groupNonmetallic character dominates in this groupNonmetallic O exists as diatomic moleculesNonmetallic O exists as diatomic moleculesNonmetallic S exists as various covalently Nonmetallic S exists as various covalently

bonded polyatomic formsbonded polyatomic formsMetalloids Se and Te are more metallic than S, Metalloids Se and Te are more metallic than S,

but bear some resemblance to Sbut bear some resemblance to SPo is even more metallic, but its behavior is not Po is even more metallic, but its behavior is not

well known since it is a rare, radioactive well known since it is a rare, radioactive elementelement

5151

Group 6AGroup 6A

Oxygen dominated by oxidation number -2Oxygen dominated by oxidation number -2The other elements have oxidation numbers The other elements have oxidation numbers

from -2 through +6, the higher ones being from -2 through +6, the higher ones being quite common, especially in combination quite common, especially in combination with oxygenwith oxygen

5252

SulfurSulfur

S found in earth's crust S found in earth's crust as sulfide and sulfate as sulfide and sulfate minerals and as the free minerals and as the free elementelement

Also a small but critical Also a small but critical constituent of plant and constituent of plant and animal tissueanimal tissue

Occurs as sulfur dioxide Occurs as sulfur dioxide and sulfur trioxide in and sulfur trioxide in the atmospherethe atmosphere Frasch processFrasch process

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SulfurSulfur

Elemental sulfur is a tasteless, Elemental sulfur is a tasteless, odorless, combustible yellow solid odorless, combustible yellow solid existing in a variety of allotropes with existing in a variety of allotropes with different molecular structuresdifferent molecular structures

Rhombic and monoclinic forms Rhombic and monoclinic forms consist of Sconsist of S88 rings rings

S8.ent

5454

SulfurSulfur

Major use of sulfur is the preparation of Major use of sulfur is the preparation of sulfuric acid, which is used primarily to sulfuric acid, which is used primarily to make phosphate fertilizers and impure make phosphate fertilizers and impure phosphoric acid from phosphate rockphosphoric acid from phosphate rock

Sulfur forms binary compounds with all the Sulfur forms binary compounds with all the elements except iodine and the noble gaseselements except iodine and the noble gases

5555

SulfurSulfur

Hydrogen sulfide (HHydrogen sulfide (H22S):S):usually prepared by reaction of a metal sulfide usually prepared by reaction of a metal sulfide

with an acidwith an acidgas well known for its "rotten-egg" odorgas well known for its "rotten-egg" odorextremely poisonousextremely poisonous largest source of sulfur in the atmospherelargest source of sulfur in the atmosphere

Sulfur reacts with oxygen to form two oxides, Sulfur reacts with oxygen to form two oxides, sulfur dioxide and sulfur trioxide, which form sulfur dioxide and sulfur trioxide, which form oxoanions (SOoxoanions (SO33

2-2- and SO and SO442-2-) and oxoacids ) and oxoacids

(H(H22SOSO33 and H and H22SOSO44) by reaction with metal ) by reaction with metal oxides or wateroxides or water

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SulfurSulfur

Sulfuric acid is a powerful dehydrating Sulfuric acid is a powerful dehydrating agent, strong acid and moderate oxidizer.agent, strong acid and moderate oxidizer.

Sulfuric acid removes HSulfuric acid removes H22O from the sugar O from the sugar

leaving a black mass of C. Steam is leaving a black mass of C. Steam is produced because the reaction is very produced because the reaction is very exothermic.exothermic.

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What are the structures of:What are the structures of:SOSO22

SOSO33

SOSO3322--

SOSO4422--

HH22SOSO33

HH22SOSO44

so2.ent

so3.ent

so3-2.ent

so4-2.ent

h2so3.ent

h2so4.ent

5858

22.7 Nitrogen22.7 Nitrogen

Electronic configuration of the Group VA Electronic configuration of the Group VA (15) elements is ns(15) elements is ns22npnp33

Little resemblance between the chemistry of Little resemblance between the chemistry of nitrogen and the other elements in this nitrogen and the other elements in this groupgroup

5959

NitrogenNitrogen

Nitrogen as an element is the colorless, Nitrogen as an element is the colorless, odorless, diatomic molecule Nodorless, diatomic molecule N22, the major , the major

constituent of airconstituent of airAn essential component of all living matter An essential component of all living matter

in protein and amino acidsin protein and amino acidsNitrogen compounds are important Nitrogen compounds are important

components of chemical fertilizerscomponents of chemical fertilizersMost uses of nitrogen involve its compounds, Most uses of nitrogen involve its compounds,

such as ammonia and nitrogen oxides.such as ammonia and nitrogen oxides.

6060


List the formulas for all the oxides that you List the formulas for all the oxides that you expect nitrogen to form.expect nitrogen to form.

6161

Preparation of NitrogenPreparation of Nitrogen

NN22 is produced by fractional distillation of is produced by fractional distillation of air.air.

Nitrogen is fixed by forming NHNitrogen is fixed by forming NH33 (Haber (Haber Process).Process).

NHNH3 3 is converted into other useful chemicals is converted into other useful chemicals (NO, NO(NO, NO22, nitrites and nitrates)., nitrites and nitrates).

6262

NitrogenNitrogen

Positive oxidation numbers of nitrogen Positive oxidation numbers of nitrogen occur in the oxides, including Noccur in the oxides, including N22O, NO, O, NO,

NN22OO33, NO, NO22, N, N22OO44, and N, and N22OO55..

Aqueous NAqueous N22OO33 is converted to nitrous acid is converted to nitrous acid

(HNO(HNO22), and N), and N22OO55 to nitric acid (HNO to nitric acid (HNO33).).

Nitrous oxide, NNitrous oxide, N22O, occurs naturally in the O, occurs naturally in the

atmosphere, as a result of the natural atmosphere, as a result of the natural degradation of proteins.degradation of proteins.

6363

NitrogenNitrogen

NN22O can be formed by thermal O can be formed by thermal

decomposition of NHdecomposition of NH44NONO33

NN22O is used as an anesthetic (in laughing gas)O is used as an anesthetic (in laughing gas)

Nitric oxide, NO, is formed by reaction of Cu Nitric oxide, NO, is formed by reaction of Cu metal with dilute aqueous nitric acid or in metal with dilute aqueous nitric acid or in high temperature combustion processes and high temperature combustion processes and in the oxidation of ammonia gas in the oxidation of ammonia gas commerciallycommercially

6464

NitrogenNitrogen

NO reacts rapidly with ONO reacts rapidly with O22 to form reddish- to form reddish-

brown NObrown NO22..

Dinitrogen trioxide results from Dinitrogen trioxide results from

reaction between NO and NOreaction between NO and NO22..

NN22OO33 is blue as a liquid. is blue as a liquid.

Gaseous NGaseous N22OO33 reacts with water to form the reacts with water to form the

weak acid, nitrous acid, HNOweak acid, nitrous acid, HNO22..

04m17vd1.mov.lnk

6565


Write an equation for the preparation of Write an equation for the preparation of nitrogen dioxide from common laboratory nitrogen dioxide from common laboratory chemicals.chemicals.

6666

NitrogenNitrogen

Nitrogen dioxide, NONitrogen dioxide, NO22, is a poisonous, reddish-, is a poisonous, reddish-

brown gas with an irritating odor, which exists brown gas with an irritating odor, which exists in equilibrium with colorless Nin equilibrium with colorless N22OO44

Dinitrogen pentoxide, NDinitrogen pentoxide, N22OO55, is a volatile low-, is a volatile low-

melting white solid; dissolved in water, it melting white solid; dissolved in water, it forms HNOforms HNO33, nitric acid, nitric acid

6767

22.8 The Other Group 5A Elements: P, As, Sb, and Bi (Pnictogens)

22.8 The Other Group 5A Elements: P, As, Sb, and Bi (Pnictogens)

Although nitrogen is found in nature Although nitrogen is found in nature primarily as unreactive Nprimarily as unreactive N22, the other , the other

elements are found only in compoundselements are found only in compoundsMetallic nature increases down the groupMetallic nature increases down the group

PPAsAs

BiBi

SbSb

6868


Predict the following properties for Predict the following properties for phosphorus:phosphorus:metallic charactermetallic charactertype of bondingtype of bondingacid/base character of oxidesacid/base character of oxidesformulas of oxidesformulas of oxides

6969

PhosphorusPhosphorus

Phosphorus is essentially nonmetallic, Phosphorus is essentially nonmetallic, forms covalent bonds and has acidic oxidesforms covalent bonds and has acidic oxides

7070


Predict the acid/base character of the oxides Predict the acid/base character of the oxides of As, Sb, and Bi, relative to those of P. of As, Sb, and Bi, relative to those of P. How can we explain the predicted trend?How can we explain the predicted trend?

7171

Group 5AGroup 5A

Arsenic has properties between those of a Arsenic has properties between those of a nonmetal and a metalloid, with amphoteric nonmetal and a metalloid, with amphoteric (though more acidic than basic) oxides(though more acidic than basic) oxides

Antimony is mostly metallic, but with some Antimony is mostly metallic, but with some properties of a metalloid, and amphoteric properties of a metalloid, and amphoteric (more basic than acidic) oxides(more basic than acidic) oxides

Bismuth, is metallic, with basic oxidesBismuth, is metallic, with basic oxidesThese trends are consistent with dramatic These trends are consistent with dramatic

decreases in ionization energy down the decreases in ionization energy down the group group

7272

Group 5AGroup 5A

Trends in oxidation number: Trends in oxidation number: N and P range from -3 to +5N and P range from -3 to +5As primarily +3 and +5As primarily +3 and +5Sb mostly +3, occasionally +5Sb mostly +3, occasionally +5Bi almost exclusively +3, rarely as +5Bi almost exclusively +3, rarely as +5

The lower, more metallic elements in the The lower, more metallic elements in the group have fewer stable oxidation numbers group have fewer stable oxidation numbers than Nthan N

7373


Phosphorus found as phosphates in 190 Phosphorus found as phosphates in 190 different minerals, most importantly different minerals, most importantly apatite, Caapatite, Ca55(PO(PO44))33OHOH

Phosphates are an important constituent of Phosphates are an important constituent of all bone tissueall bone tissue

7474


Mainly occurs in phosphorus Mainly occurs in phosphorus minerals (e.g. phosphate rock, minerals (e.g. phosphate rock, CaCa33(PO(PO44))22).).

Elemental PElemental P44 produced by produced by reductionreduction

2 Ca2 Ca33(PO(PO44))22((ss) + 6SiO) + 6SiO22((ss) + 10C() + 10C(ss) ) P P44((gg) + 6CaSiO) + 6CaSiO33((ll) + 10CO() + 10CO(gg))

Phosphoric acid, made from Phosphoric acid, made from phosphate rock, is one of the phosphate rock, is one of the ingredients in Coca-Cola.ingredients in Coca-Cola.

7575


Phosphorus occurs as 19 allotropes, the Phosphorus occurs as 19 allotropes, the principal ones being white (tetrahedral Pprincipal ones being white (tetrahedral P44), ),

red, and black phosphorusred, and black phosphorus

7676


White phosphorus is a soft solid, with White phosphorus is a soft solid, with molecules held together by weak molecules held together by weak intermolecular forces.intermolecular forces.

White phosphorus is poisonous and causes White phosphorus is poisonous and causes painful skin burns.painful skin burns.

White phosphorus is quite reactive and White phosphorus is quite reactive and ignites spontaneously in airignites spontaneously in air

Barking DogsBarking Dogsbarking_dogs.mov.lnkChmvid15.mov.lnkwrite_p4.mov.lnk V00022.mov.lnk

7777


Red phosphorus is an amorphous solid Red phosphorus is an amorphous solid formed by heating white phosphorusformed by heating white phosphorus

Red phosphorus involves PRed phosphorus involves P44 tetrahedral tetrahedral

molecules bonded to one another in long molecules bonded to one another in long chainschains

Black phosphorus is still less reactiveBlack phosphorus is still less reactiveBlack phosphorus may be amorphous or Black phosphorus may be amorphous or

have a graphite-like structure; it is metallic have a graphite-like structure; it is metallic in appearance and an electrical conductorin appearance and an electrical conductor

7878


What acids are formed when the oxides, What acids are formed when the oxides, PP44OO66 and P and P44OO1010, are reacted with excess , are reacted with excess

water?water?

7979


Two oxides of phosphorus, PTwo oxides of phosphorus, P44OO66 and P and P44OO1010, ,

formed by burning phosphorusformed by burning phosphorusReact with water to form phosphorous acid, React with water to form phosphorous acid,

HH33POPO33 and phosphoric acid, H and phosphoric acid, H33POPO44

PP44OO1010 is used as a drying agent because of is used as a drying agent because of

its affinity for water.its affinity for water.

p4o6.ent

p4o10.ent

8080

22.9 Carbon22.9 Carbon

Carbon constitutes about 0.027 % of the Carbon constitutes about 0.027 % of the earth’s crust.earth’s crust.

Carbon is the main constituent of living Carbon is the main constituent of living matter.matter.

Study of carbon compounds is called organic Study of carbon compounds is called organic chemistry.chemistry.

8181

CarbonCarbon

Carbon forms more compounds than all Carbon forms more compounds than all other elements except hydrogen; typical other elements except hydrogen; typical compounds are the hydrocarbons and their compounds are the hydrocarbons and their derivativesderivatives

8282

CarbonCarbon

Exists as diamond, graphite, and an Exists as diamond, graphite, and an amorphous form, as well as the recently amorphous form, as well as the recently discovered allotrope Cdiscovered allotrope C6060, called , called

buckminsterfullerenebuckminsterfullerene

8383

CarbonCarbon

Diamond: clear crystalline form of carbon, Diamond: clear crystalline form of carbon, one of the hardest substances known, can be one of the hardest substances known, can be synthesized from graphite with high synthesized from graphite with high temperature and pressure and a metal temperature and pressure and a metal catalystcatalyst

8484


Why is diamond so hard, while graphite is Why is diamond so hard, while graphite is soft and slippery, even though both are soft and slippery, even though both are pure carbon?pure carbon?

8585

CarbonCarbon

Graphite: Graphite: slippery gray-black solidslippery gray-black solidstrong covalent bonds hold atoms together in strong covalent bonds hold atoms together in

each layer, but the layers are bonded only by each layer, but the layers are bonded only by weak van der Waals forces, so the layers slide weak van der Waals forces, so the layers slide across one another readilyacross one another readily

found widely distributed in the earth's crust found widely distributed in the earth's crust and synthesized from amorphous carbonand synthesized from amorphous carbon

graphit3.ent

8686

CarbonCarbon

Uses of graphite:Uses of graphite:cruciblescrucibles lubricantslubricantspencilspencilsnuclear reactors (to slow down fast neutrons)nuclear reactors (to slow down fast neutrons)electrodes for electrolysis reactionselectrodes for electrolysis reactions

8787

CarbonCarbon

Amorphous carbon: Amorphous carbon: carbon blackscarbon blackscharcoalcharcoalactivated carbonactivated carbonsootsootcokecoke

Essentially microcrystalline forms of Essentially microcrystalline forms of graphite with no layeringgraphite with no layering

Formed by thermal decomposition or partial Formed by thermal decomposition or partial decomposition of coal, petroleum, natural decomposition of coal, petroleum, natural gas, and wood with an insufficient supply of gas, and wood with an insufficient supply of oxygenoxygen

8888

CarbonCarbon

Amorphous carbon:Amorphous carbon:burning oil gives lampblackburning oil gives lampblackheating coal in the absence of air produces cokeheating coal in the absence of air produces cokeheating wood in the absence of air gives heating wood in the absence of air gives

charcoalcharcoalCarbon black used as a filler in rubber tires Carbon black used as a filler in rubber tires

to increase toughness and prevent to increase toughness and prevent brittlenessbrittleness

Lampblack used in inks, paints, coating on Lampblack used in inks, paints, coating on carbon papercarbon paper

8989

CarbonCarbon

Charcoal used Charcoal used in filters to adsorb odorsin filters to adsorb odors in gas masks to adsorb poisonous gasesin gas masks to adsorb poisonous gases in the decolorizing of sugarin the decolorizing of sugar in water treatmentin water treatment in the reclamation of dry-cleaning solventsin the reclamation of dry-cleaning solvents

Coke used in the extraction of metals from Coke used in the extraction of metals from their oxide orestheir oxide ores

Vd22_012.mov.lnk

9090

CarbonCarbon

Buckminsterfullerene consists of molecules Buckminsterfullerene consists of molecules of Cof C6060 formed by laser or high-temperature formed by laser or high-temperature

carbon arc vaporization of graphitecarbon arc vaporization of graphiteOne member of a class of new forms of One member of a class of new forms of

carbon called fullerenes, which consist of carbon called fullerenes, which consist of clusters of carbon atoms containing even clusters of carbon atoms containing even numbers from 44 to 84numbers from 44 to 84

9191

Fullerenes in SolutionFullerenes in Solution

9292

CarbonCarbon

CC6060 exists as a truncated icosahedron, which exists as a truncated icosahedron, which

contains 12 pentagonal faces and 20 contains 12 pentagonal faces and 20 hexagonal faceshexagonal faces

Remarkable physical stability, but Remarkable physical stability, but chemically reactivechemically reactive

Now being prepared as tubes, into which Now being prepared as tubes, into which metals can be inserted. These are the metals can be inserted. These are the thinnest capillary tubes known.thinnest capillary tubes known.

9393

CarbonCarbon

Elemental carbon is relatively unreactive at Elemental carbon is relatively unreactive at room temperatureroom temperature

Insoluble in water, dilute acids and bases, Insoluble in water, dilute acids and bases, and organic solventsand organic solvents

At high temperatures, carbon becomes At high temperatures, carbon becomes highly reactive and combines directly with highly reactive and combines directly with many elements, including oxygenmany elements, including oxygen

Carbon at high temperatures also reduces Carbon at high temperatures also reduces water, metal oxides, oxoanions (e.g., water, metal oxides, oxoanions (e.g., phosphate in phosphate rock), hydrogenphosphate in phosphate rock), hydrogen

9494

Oxides of CarbonOxides of CarbonOxides of CarbonOxides of Carbon

Carbon forms CO and COCarbon forms CO and CO22..CO is very toxic (binds irreversibly to Fe in CO is very toxic (binds irreversibly to Fe in

hemoglobin, causing respiratory arrest).hemoglobin, causing respiratory arrest).CO also has a lone pair on C, which is unusual.CO also has a lone pair on C, which is unusual.CO is a good Lewis baseCO is a good Lewis base

Ni(CO)Ni(CO)44 forms when Ni is warmed in CO forms when Ni is warmed in COCO can be used as a fuel CO can be used as a fuel

2CO(2CO(gg) + O) + O22((gg) ) 2CO 2CO22((gg) ) HH = -566 kJ = -566 kJCO is a good reducing agentCO is a good reducing agent

FeFe33OO44((ss) + 4CO() + 4CO(gg) ) 3Fe( 3Fe(ss) + 4CO) + 4CO22((gg))

9595


COCO22 is produced when organic is produced when organic

compounds are burned in oxygen:compounds are burned in oxygen:

C(C(ss) + O) + O22((gg) ) CO CO22((gg))

CHCH44((gg) + 2O) + 2O22((gg) ) CO CO22((gg) + 2H) + 2H22O(O(ll))

CC22HH55OH(OH(ll) + 3O) + 3O22((gg) ) 2CO 2CO22((gg) + ) +

3H3H22O(O(ll))

COCO22 is produced by treating is produced by treating

carbonates with acid. carbonates with acid.

9696


Fermentation of sugar to produce alcohol also Fermentation of sugar to produce alcohol also produces COproduces CO22::

CC66HH1212OO66((aqaq) ) 2C 2C22HH55OH(OH(aqaq) + 2CO) + 2CO22((gg))

At atmospheric pressure, COAt atmospheric pressure, CO22 condenses to condenses to

form COform CO22((ss) or dry ice.) or dry ice.

COCO22 is used as dry ice (refrigeration), is used as dry ice (refrigeration),

carbonation of beverages, washing soda carbonation of beverages, washing soda (Na(Na22COCO33.10H.10H22O) and baking soda O) and baking soda

(NaHCO(NaHCO33.10H.10H22O).O).

9797

Carbonic Acid and Carbonic Acid and CarbonatesCarbonates


When COWhen CO22 dissolves in water (moderately dissolves in water (moderately soluble) carbonic acid forms:soluble) carbonic acid forms:

COCO22((aqaq) + H) + H22O(O(ll) ) ⇌⇌ H H22COCO33((aqaq))Carbonic acid is responsible for giving Carbonic acid is responsible for giving

carbonated beverages a sharp acidic taste.carbonated beverages a sharp acidic taste.Partial neutralization of HPartial neutralization of H22COCO33 gives gives

hydrogen carbonates (bicarbonates) and hydrogen carbonates (bicarbonates) and full neutralization gives carbonates.full neutralization gives carbonates.

Many minerals contain COMany minerals contain CO332-2-..

B32.mov.lnk

9898



At elevated temperatures CaCOAt elevated temperatures CaCO33 decomposes: decomposes:

CaCOCaCO33((ss) ) CaO( CaO(ss) + 2CO) + 2CO22((gg))This reaction is the commercial source of lime, This reaction is the commercial source of lime,

CaO.CaO.CaO reacts with water and COCaO reacts with water and CO22 to form to form

CaCOCaCO33 which binds the sand in mortar: which binds the sand in mortar:

CaO(CaO(ss) + H) + H22O(O(ll) Ca) Ca2+2+((aqaq) + 2OH) + 2OH--((aqaq))

CaCa2+2+((aqaq) + 2OH) + 2OH--((aqaq) + CO) + CO22((aqaq) ) CaCO CaCO33((ss) + ) + HH22O(O(ll))

9999

CarbidesCarbides

Carbon combines with elements with a Carbon combines with elements with a lower electronegativity to form carbides, lower electronegativity to form carbides, which exist in three classeswhich exist in three classes

Salt-like carbides form with the most Salt-like carbides form with the most electropositive metals and are ionic, so they electropositive metals and are ionic, so they are hydrolyzed by water or dilute acid to are hydrolyzed by water or dilute acid to give hydrocarbonsgive hydrocarbons

100100

CarbidesCarbides

Interstitial carbides are formed with Interstitial carbides are formed with transition metals, are very hard and have transition metals, are very hard and have very high melting points, high metallic very high melting points, high metallic conductivity, and metallic luster; they conductivity, and metallic luster; they consist of a metal with carbon atoms consist of a metal with carbon atoms located in some of the interstitial sites (or located in some of the interstitial sites (or holes) in the metal structureholes) in the metal structure

101101

CarbidesCarbides

Covalent carbides include those of silicon Covalent carbides include those of silicon and boron, which are close in size and and boron, which are close in size and electronegativity to carbon; they are electronegativity to carbon; they are completely covalent and form infinite completely covalent and form infinite network structures, are exceptionally hard network structures, are exceptionally hard materials widely used as abrasivesmaterials widely used as abrasives

102102

22.10 The Other Group 4A Elements: Si, Ge, Sn, and Pb22.10 The Other Group 4A

Elements: Si, Ge, Sn, and Pb

SiSi SnSn

103103

General Characteristics of General Characteristics of Group 4A ElementsGroup 4A Elements

General Characteristics of General Characteristics of Group 4A ElementsGroup 4A Elements

The electronegativities are low.The electronegativities are low.The dominant oxidation state for Ge, Sn and The dominant oxidation state for Ge, Sn and

Pb is +2.Pb is +2.Carbon has a coordination number of 4, the Carbon has a coordination number of 4, the

other members have higher coordination other members have higher coordination numbers.numbers.

C-C bonds are very strong, so C tends to C-C bonds are very strong, so C tends to form long chains.form long chains.

Because the Si-O bond is stronger than the Because the Si-O bond is stronger than the Si-Si bond, Si tends to form oxides (silicates).Si-Si bond, Si tends to form oxides (silicates).

104104


Compare the following properties on going Compare the following properties on going down Group 4A:down Group 4A:Metallic characterMetallic characterIonization energiesIonization energiesMelting pointsMelting pointsAcid/base nature of oxidesAcid/base nature of oxides

105105

Group 4AGroup 4A

Si is nonmetallic/metalloid with only some Si is nonmetallic/metalloid with only some of its chemistry similar to carbonof its chemistry similar to carbon

Ge is a metalloidGe is a metalloidSn and Pb are metallicSn and Pb are metallic Ionization energies and melting points Ionization energies and melting points

decrease down the group, reflecting the decrease down the group, reflecting the change from nonmetal to metal change from nonmetal to metal

106106

Group QuizGroup Quiz

Write a formula for the Write a formula for the acidacid, if any, that would , if any, that would be formed by reaction of these oxides with be formed by reaction of these oxides with water:water:COCO22

COCOCaOCaOSOSO33

PP44OO1010

Hint: You should have three formulas.Hint: You should have three formulas.

107107

Group 4AGroup 4A

Carbon bonds readily to itselfCarbon bonds readily to itselfThis tendency diminishes on going down the This tendency diminishes on going down the

group because the bond strength decreases group because the bond strength decreases considerably as the elements get largerconsiderably as the elements get larger

Oxidation number +4 dominates near the Oxidation number +4 dominates near the top of the group, +2 becomes more stable top of the group, +2 becomes more stable down the groupdown the group

108108

SiliconSilicon

Silicon exists in the earth's Silicon exists in the earth's crust as silicon dioxide and crust as silicon dioxide and over 800 silicate mineralsover 800 silicate minerals

Elemental silicon obtained Elemental silicon obtained by reduction of SiOby reduction of SiO22 with with

C or CaCC or CaC22 at high at high

temperature, purified by temperature, purified by zone refiningzone refiningSiOSiO22((ll) + 2C() + 2C(ss) ) Si( Si(ll) + 2CO() + 2CO(gg))

109109

SiliconSilicon

Silicon: Silicon: brittle gray-black metallic-looking solidbrittle gray-black metallic-looking solidquite hardquite hardhigh melting pointhigh melting pointdiamond-like tetrahedral network structurediamond-like tetrahedral network structure inert at room temperature but reactive at high inert at room temperature but reactive at high

temperaturestemperatures

Used in semiconductor devicesUsed in semiconductor devices

si.ent

110110

SiliconSilicon

Silicon hydrides or silanes arise from Silicon hydrides or silanes arise from reaction of Mgreaction of Mg22Si with acids, giving a Si with acids, giving a

mixture of SiHmixture of SiH44, Si, Si22HH66, Si, Si33HH88, Si, Si44HH1010, Si, Si55HH1212, ,

and Siand Si66HH1414

111111


What is the structure and bonding for What is the structure and bonding for SiSi22HH66??

112112

SiliconSilicon

Silanes are quite reactive:Silanes are quite reactive:The first two are stable.The first two are stable.The others decompose to give SiHThe others decompose to give SiH44, Si, Si22HH66, and , and

HH22..

Much more reactive than the corresponding Much more reactive than the corresponding alkanes because of the availability of empty 3d alkanes because of the availability of empty 3d orbitals that can be used to form bonds with orbitals that can be used to form bonds with another reactantanother reactant

They are spontaneously flammable in air.They are spontaneously flammable in air.

113113


SiOSiO22, found as quartz, is quite hard. What , found as quartz, is quite hard. What

feature of its structure gives rise to this feature of its structure gives rise to this hardness? hardness?

RoseRoseQuartzQuartz

114114

SiliconSilicon

SiOSiO22 exists as polymeric (SiO exists as polymeric (SiO22))nn, which has , which has silicon covalently bonded to four bridging silicon covalently bonded to four bridging oxygen atoms.oxygen atoms.

Extended covalent bonding networkExtended covalent bonding networkHard, high-melting solidHard, high-melting solid

AmethystAmethyst Smoky QuartzSmoky Quartzsio2.ent

115115

SiliconSilicon

Glass is formed by heating Glass is formed by heating together silicon dioxide, alkali together silicon dioxide, alkali metal and alkaline earth metal and alkaline earth metal oxides, and sometimes metal oxides, and sometimes other oxides, the particular other oxides, the particular mixture controlling the mixture controlling the properties of the glass.properties of the glass.

Silicate structure is somewhat Silicate structure is somewhat random in contrast to random in contrast to crystalline silicatescrystalline silicates

116116

SiliconSilicon

Some bonds are under more strain than Some bonds are under more strain than others, so the glass melts over a range of others, so the glass melts over a range of temperatures and can be softened without temperatures and can be softened without meltingmelting

117117

SiliconSilicon

90 % of the earth’s crust is composed of 90 % of the earth’s crust is composed of compounds of Si and O.compounds of Si and O.

Silicates are compounds where Si has four Silicates are compounds where Si has four O atoms surrounding it in a tetrahedral O atoms surrounding it in a tetrahedral arrangement.arrangement.

The oxidation state of Si is +4.The oxidation state of Si is +4.The silicate tetrahedra are building blocks The silicate tetrahedra are building blocks

for more complicated structures.for more complicated structures.

118118

SiliconSilicon

Many silicates naturally with the basic Many silicates naturally with the basic structural unit being the SiOstructural unit being the SiO44 tetrahedron tetrahedron occurring in several varieties: occurring in several varieties: singlysinglysmall groups sharing oxygen atomssmall groups sharing oxygen atomssmall cyclic groupssmall cyclic groups infinite chainsinfinite chainsdouble-stranded chains (or bands)double-stranded chains (or bands) infinite sheetsinfinite sheets

These few structures form many hundreds of These few structures form many hundreds of minerals by combination of silicate anions minerals by combination of silicate anions with metal cations.with metal cations.

119119

Silicate MineralsSilicate Minerals

120120


121121


122122


123123

SiliconSilicon

The silicate structure is reflected in the The silicate structure is reflected in the physical structure of minerals such as mica physical structure of minerals such as mica and asbestos.and asbestos.

124124

22.11 Boron22.11 Boron

Black crystalline element, extremely hard Black crystalline element, extremely hard and brittle, low density, high melting point and brittle, low density, high melting point and boiling point, low electrical and boiling point, low electrical conductivity (so classified as a conductivity (so classified as a semiconductor), used in semiconductor semiconductor), used in semiconductor electronics and added to steel to increase electronics and added to steel to increase strength and to copper to increase electrical strength and to copper to increase electrical conductivityconductivity

125125

BoronBoron

Similarities of some properties to those of Similarities of some properties to those of carbon, of others to those of silicon (due to carbon, of others to those of silicon (due to the diagonal relationship leading to similar the diagonal relationship leading to similar size and electronegativity)size and electronegativity)

Carbon, silicon, and boron all form Carbon, silicon, and boron all form covalently-bonded extended network solids covalently-bonded extended network solids and covalent halidesand covalent halides

126126

BoronBoron

Occurs in deposits of borax, Occurs in deposits of borax, NaNa22BB44OO77

..10H10H22OO

Borax used as an additive to laundry Borax used as an additive to laundry detergents to soften the water.detergents to soften the water.

Which U.S. president was associated Which U.S. president was associated with Twenty Mule Team Borax?with Twenty Mule Team Borax?

Boron recovered by acidifying, heating, Boron recovered by acidifying, heating, and reduction of the resulting oxide by and reduction of the resulting oxide by heating with Mg, purified by zone refiningheating with Mg, purified by zone refining

127127

BoronBoron

Resembles metals in its physical properties Resembles metals in its physical properties but is more like nonmetals chemicallybut is more like nonmetals chemically

Chemical behavior is complex and unusual: Chemical behavior is complex and unusual: ionization energy is unusually high, so ionization energy is unusually high, so formation of a cation is difficult, high formation of a cation is difficult, high electronegativity (comparable to nonmetals)electronegativity (comparable to nonmetals)

All its compounds are covalentAll its compounds are covalent

128128


What is the valence electron configuration What is the valence electron configuration of boron? How many covalent bonds will it of boron? How many covalent bonds will it normally form?normally form?

129129

BoronBoron

Valence electron configuration 2sValence electron configuration 2s222p2p11, so , so forms only three normal covalent bonds, forms only three normal covalent bonds, but electron deficiency makes it a good but electron deficiency makes it a good Lewis acidLewis acid

Oxidation number +3 common, but others Oxidation number +3 common, but others found in boranesfound in boranes

BB33++ does not exist in aqueous solution. Why does not exist in aqueous solution. Why not?not?

130130

BoronBoron

Reacts with FReacts with F22 and Cl and Cl22 to give trihalides to give trihalides

Great affinity for OGreat affinity for O22, which is used to , which is used to

remove oxygen from metal oxides to purify remove oxygen from metal oxides to purify molten metalsmolten metals

bf3.ent

09m07an1.mov.lnk

131131

BoronBoron

B reacts with NB reacts with N22 at high at high

temperature to give solid temperature to give solid BN.BN.

BN is very stable due to its BN is very stable due to its graphite-like structure, graphite-like structure, which arises from the which arises from the presence of only 3 valence presence of only 3 valence electrons and the tendency electrons and the tendency to use spto use sp22 hybrid orbitals. hybrid orbitals.

132132

BoronBoron

BN is also known in a BN is also known in a diamond-like diamond-like structure, which is structure, which is formed by application formed by application of high temperature of high temperature and pressure, and is and pressure, and is extremely hard and is extremely hard and is used as an abrasive.used as an abrasive.

133133

BoronBoron

Large number of hydrides have been Large number of hydrides have been preparedprepared

BHBH33 is known but very unstable (reactive) is known but very unstable (reactive)

Simplest stable one is diborane, BSimplest stable one is diborane, B22HH66, which , which

decomposes to other boranes, e.g. Bdecomposes to other boranes, e.g. B55HH99, ,

when heatedwhen heated

b2h6.ent b5h9.ent

134134

BoronBoron

Unusual structure and bonding in the boranes, in Unusual structure and bonding in the boranes, in which hydrogens act as bridges between boron which hydrogens act as bridges between boron and the B-H-B arrangement shares two electrons and the B-H-B arrangement shares two electrons between three atoms (called three center between three atoms (called three center bonding) bonding)

Because of their electron deficiencies, boranes Because of their electron deficiencies, boranes are highly reactive are highly reactive

Diborane is very reactive:Diborane is very reactive:

BB22HH66((gg) + 3O) + 3O22((gg) ) B B22OO33((ss) + 3H) + 3H22O(O(gg))

HH = -2030 kJ = -2030 kJ

135135

BoronBoron

Some boranes are reactive (BSome boranes are reactive (B55HH99) while ) while

some are stable in air at room temperature some are stable in air at room temperature (B(B1010HH1414).).

BB22OO33 is the only important boron oxide. is the only important boron oxide.

Boric acid, HBoric acid, H33BOBO33 or B(OH) or B(OH)33 is a weak acid is a weak acid

(K(Kaa = 5.8 = 5.8 10 10-10-10).).

Boric acid is used as an eye wash.Boric acid is used as an eye wash.

1 chapter 22 chemistry of the nonmetals ldescriptive chemistry of the elements is consistent with...

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