chapter 3: elements, compounds, and the periodic table chemistry: the molecular nature of matter, 6e...

Chapter 3: Elements, Compounds,and the Periodic Table

Chemistry: The Molecular Nature of Matter, 6E

Jespersen/Brady/Hyslop

Jespersen/Brady/Hyslop Chemistry: The Molecular Nature of Matter, 6E

Discovery of Subatomic Particles Late 1800s & early 1900s

Cathode ray tube experiments showed that atoms are made up of subatomic particles

Discovered negatively charged particles moving from Cathode – negative electrode to Anode – positive electrode

2


Discovery of ElectronJJ Thomson (1897) Modified cathode ray tube Made quantitative

measurements on cathode rays

Discovered negatively charged particles Electrons (e)

Determined charge to mass ratio (e/m) of these particles e/m = 1.76 x 108 coulombs/gram

3


Millikan Oil Drop Experiment Determining charge on Electron Calculated charge on electron

e = 1.60 x 1019 C

Combined with Thomson’s experiment to get mass of electron m = 9.09 x 1028 g

4


Discovery of Atomic NucleusRutherford’s Alpha Scattering Experiment

Most alpha () rays passed right through gold A few were deflected off at an angle 1 in 8000 bounced back towards alpha ray

source Gave us current model of nuclear atom

5


Discovery Of Proton Discovered in 1918 in Ernest Rutherford’s

lab Detected using Mass Spectrometer

Hydrogen had mass 1800x mass of electron Masses of other gases whole number multiples

of mass of hydrogen

Proton Smallest

positively charged particle

6


Rutherford’s Nuclear Atom Demonstrated that nucleus:

has almost all of mass in atom has all of positive charge is located in very small volume at center of

atom

Very tiny, extremely dense core of atom Where protons (p+) &

neutrons (1n) are located

7


Atomic Structure Electrons (e)

Very low mass Occupy most of atom’s space

Balance of attractive & repulsive forces controls atom size

Attraction between protons (p+) & electrons (e) holds electrons around nucleus

Repulsion between electrons helps them spread out over volume of atom

In neutral atom Number of es must equal number of p+s Diameter of atom ~10,000 × diameter of

nucleus8


Discovery of Neutron (1n) First postulated by Rutherford & coworkers

Estimated number of positive charges on nucleus based on experimental data

Nuclear mass based on this number of protons always far short of actual mass About ½ actual mass

Therefore, must be another type of particle Has mass about same as proton Electrically neutral

Discovered in 1932 by Chadwick Caused free neutron to be created

9


10

Properties of Subatomic Particles

Particle Mass (g)Electrical Charge

Symbol

Electron

9.10939102

8 1

Proton1.67264102

4 +1

Neutron1.67495102

4 0

e01

p1111 ,H

n10

3 Kinds of subatomic particles of principal interest to Chemists

Nucleus (protons + neutrons)

Electrons


Atomic NotationAtomic number (Z) Number of protons that atom has in nucleus

Unique to each type of element Element is substance whose atoms all contain

identical number of protons

Z = # protonsIsotopes Atoms of same element with different

masses Same number of protons ( ) Different number of neutrons ( )

11

p11

n01


Atomic NotationIsotope Mass number (A)

A = (# protons) + (# neutrons) A = Z + N For charge neutrality, number of electrons &

protons must be equal

Atomic Symbols Summarize information about subatomic

particles Every isotope defined by 2 numbers Z & A Symbolized by

Ex. What is the atomic symbol for helium? He has 2 e–, 2 n & 2 p+ Z = 2, A = 4

12

XAZ

He42


Isotopes Most elements are mixtures of 2 or more

stable isotopes Each isotope has slightly different mass Chemically, isotopes have virtually identical

chemical properties Relative proportions of different isotopes are

essentially constant Isotopes distinguished by mass number (A):

Ex. 3 isotopes of hydrogen (H) 4 isotopes of iron (Fe)

13


Example:What is the isotopic symbol for Uranium-

235? Number of protons (p+) = 92

= number of electrons in neutral atom Number of neutrons (1n) = 143 Atomic number (Z) = 92 Mass number (A) = 92 + 143 = 235 Chemical symbol = U

Summary for uranium-235:

14

U23592


15

Learning Check:

Fill in the blanks:symbol neutrons protons electrons60Co 81Br

36 29 29

33 27 27

46 35 35

Cu6529


Your Turn!

An atom of has ___ protons, ___ neutrons, and ___ electrons.A. 82, 206, 124

B. 124, 206, 124

C. 124, 124, 124

D. 82, 124, 82

E. 82, 124, 124

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20682Pb


Carbon-12 Atomic Mass Scale Need uniform mass scale for atoms

Atomic mass units (symbol u) Based on carbon: 1 atom of carbon-12 = 12 u (exactly) 1 u = 1/12 mass 1 atom of carbon-12

(exactly)

Why was 12C selected? Common Most abundant isotope of carbon All atomic masses of all other elements ~ whole

numbers Lightest element, H, has mass ~1 u

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Calculating Atomic Mass Generally, elements are mixtures of isotopes

Ex. HydrogenIsotope Mass %Abundance

1H 1.007825 u 99.985

2H 2.0140 u 0.015

How do we define Atomic Mass? Average of masses of all stable isotopes of given

element

How do we calculate Average Atomic Mass? Weighted average. Use Isotopic Abundances & isotopic masses

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Learning CheckNaturally occurring magnesium is a mixture of 3 isotopes; 78.99% of the atoms are 24Mg (atomic mass, 23.9850 u), 10.00% of 25Mg (atomic mass, 24.9858 u), and 11.01% of 26Mg (atomic mass, 25.9826 u). From these data calculate the average atomic mass of magnesium.

0.7899 * 23.9850 u = 18.946 u 24Mg

Total mass of average atom = 24.3053 u rounds up to 24.31 u

0.1000 * 24.9858 u = 2.4986 u 25Mg0.1101 * 25.9826 u = 2.8607 u 26Mg


Your Turn!A naturally occurring element consists of two isotopes. The data on the isotopes:

isotope #1 68.5257 u 60.226%

isotope #2 70.9429 u 39.774%

Calculate the average atomic mass of this element.

A.70.943 u

B.69.487 u

C.69.526 u

D.69.981 u

E.69.734 u20

0.60226 * 68.5257 u = 41.270 u0.39774 * 70.9429 u = 28.217 u

69.487 u


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Periodic Table Summarizes periodic properties of elements

Early Versions of Periodic Tables Arranged by increasing atomic mass Mendeleev (Russian) & Meyer (German) in

1869 Noted repeating (periodic) properties

Modern Periodic Table Arranged by increasing atomic number (Z): Rows called periods Columns called groups or families

Identified by numbers 1 – 18 standard international 1A – 8A longer columns & 1B – 8B shorter columns


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Modern Periodic Tablewith group labels and chemical families identified

Note: Placement of elements 58 – 71 and 90 – 103 saves space

Actinides


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A groups—Longer columns Alkali Metals

1A = first group Very reactive All Metals except for H Tend to form +1 ions React with oxygen

Form compounds that dissolve in water Yield strongly caustic or alkaline solution

(M2O)

Representative/Main Group Elements



A groups—Longer columns Alkaline Earth Metals

2A = second group Reactive Tend to form +2 ions Oxygen compounds are strongly alkaline

(MO) Many are not water soluble Accumulate in ground

24



A groups—Longer columns Halogens

7A = next to last group on right Reactive Form diatomic molecules in elemental

state 2 gases 1 liquid 2 solids

Form –1 ions with alkali metals—salts25



A groups—Longer columns Noble Gases

8A = last group on right Inert—very unreactive Only heavier elements of group react & then

very limited Don’t form charged ions Monatomic gases

26


27

B groups—shorter columns All are metals In center of table Begin in fourth row Tend to form ions with several different

charges

Ex. Fe2+ and Fe3+ Cu+ and Cu2+

Mn2+, Mn3+, Mn4+, Mn5+, Mn6+, Mn7+

Note: Last 3 columns all have 8B designation

Transition Elements


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Lanthanide elements Elements 58 – 71

Actinide elements Elements 90 – 103 At bottom of periodic table Tend to form +2 and +3 ions. All Actinides are radioactive

Inner Transition Elements


Metals, Nonmetals, or Metalloids Elements break down into 3 broad categories

Organized by regions of periodic table

Metals Left-hand side Sodium, lead, iron, gold

Nonmetals Upper right hand corner Oxygen, nitrogen, chlorine

Metalloids Diagonal line between metals & nonmetals Boron to astatine

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30

Metals, Nonmetals, or Metalloids


31

Metals Most elements in periodic tableProperties Metallic luster

Shine or reflect light Malleable

Can be hammered or rolled into thin sheets

Ductile Can be drawn into wire

Hardness Some hard – iron & chromium Some soft – sodium, lead, copper


32

Properties of Metals Conduct heat & electricity Solids at Room Temperature

Melting points (mp) > 25 °C Hg only liquid metal (mp = –39 °C) Tungsten (W) (mp = 3400 °C)

Highest known for metal

Chemical reactivity Varies greatly

Au, Pt very unreactive Na, K very reactive


33

Nonmetals 17 elements

Upper right hand corner of periodic table Exist mostly as compounds rather than as

pure elements Many are Gases

Monatomic (Noble) He, Ne, Ar, Kr, Xe, Rn Diatomic H2, O2, N2, F2, Cl2

Some are Solids: I2, Se8, S8, P4, C

3 forms of Carbon (graphite, coal, diamond)

One is liquid: Br2


34

Properties of Nonmetals Brittle

Pulverize when struck Insulators

Non-conductors of electricity and heat

Chemical reactivity Some inert

Noble gases Some reactive

F2, O2, H2

React with metals to form ionic compounds


35

Metalloids 8 Elements

Located on diagonal line between metals & nonmetals

B, Si, Ge, As, Sb, Te, Po, At

Properties Between metals & nonmetals

Metallic shine Brittle like nonmetal

Semiconductors Conduct electricity But not as well as metals Silicon (Si) & germanium (Ge)


36

Your Turn!

Which of the following statements is correct?

A.Cu is a representative transition elementB.Na is an alkaline earth metalC.Al is a semimetal in group IIIAD.F is a representative halogenE.None of these are correct


Your Turn!All of the following are characteristics of metals except:

A.Malleable

B.Ductile

C.Lustrous

D.Good conductors of heat

E.Tend to gain electrons in chemical reactions

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Ions & Ionic CompoundsIons

Transfer of 1 or more electrons from 1 atom to another

Form electrically charged particles

Ionic compound Compound composed of ions Formed from metal & nonmetal Infinite array of alternating Na+ & Cl ions

Formula unit Smallest neutral unit of ionic compound Smallest whole-number ratio of ions

38


39

Formation of Ionic CompoundsMetal + Non-metal ionic

compound 2Na(s) + Cl2(g) 2NaCl(s)

Na+ + ClNa + Cl NaCl(s)

e


40

Ionic CompoundsCations

Positively charged ions Formed from metals Atoms lose electrons

Ex. Na has 11 e– & 11 p+

Anions Negatively charged ions Formed from non-metals Atoms gain electrons

Ex. Cl has 17 e– & 17 p+

Na+ has 10 e– & 11 p+

Cl– has 16 e– & 17 p+


Experimental Evidence for Ions

Electrical conductivity requires charge movement

Ionic compounds: Do not conduct electricity in solid state Do conduct electricity in liquid & aqueous states

where ions are free to move

Molecular compounds: Do not conduct electricity in any state Molecules are comprised of uncharged particles

41


Ions of Representative Elements

42

Can use periodic table to predict ion charges

When we use North American numbering of groups: Cation positive charge = group #


43

Ions of Representative Elements

N O F Ne

Noble gases are especially stable

Nonmetals Negative () charge on anion = # spaces

you have to move to right to get to noble gas

Expected charge on O is Move 2 spaces to right O2–

What is expected charge on N? Move 3 spaces to right N3 –


44

Rules For Writing Ionic Formulas1. Cation given first in formula

2. Subscripts in formula must produce electrically neutral formula unit

3. Subscripts must be smallest whole numbers possible

Divide by 2 if all subscripts are even May have to repeat several times

4. Charges on ions not included in finished formula unit of substance

If no subscript, then 1 implied


Determining Ionic FormulasEx. Formula of ionic compound formed

when magnesium reacts with oxygen Mg is group 2A

Forms +2 ion or Mg2+ O is group 6A

Forms –2 ion or O2–

To get electrically neutral particle need 1:1 ratio of Mg2+ & O2–

Formula: MgO

45


46

Determining Ionic Formulas

“Criss-cross” rule Make magnitude of charge on one ion

into subscript for other When doing this, make sure that

subscripts are reduced to lowest whole number.

Ex. What is the formula of ionic compound formed between aluminum & oxygen ions? Al2O3Al3+ O2–


Your Turn!Which of the following is the correct formula for the formula unit composed of potassium and oxygen ions?

A.KO

B.KO2

C.K2O

D.P2O3

E.K2O2


Your Turn!Which of the following is the correct formula for the formula unit composed of Fe3+ and sulfide ions?

A.FeS

B.Fe3S2

C.FeS3

D.Fe2S3

E.Fe4S6


Cations of Transition MetalsTransition metals

Center (shorter) region of periodic table Much less reactive than group 1A & 2A Still transfer electrons to nonmetals to form ionic compounds # of electrons transferred less clear Form more than 1 positive ion Can form more than 1

compound with same non-metal

Ex. Fe + Cl

FeCl2 & FeCl3

49


Cations of Post-transition MetalsPost-transition metals

9 metals Ga, In, Sn, Tl, Pb, Bi, Uut, Uuq, Uub After transition metals & before metalloids 2 very important ones – tin (Sn) & lead (Pb)

Both have 2 possible oxidation states Both form 2 compounds with same nonmetal

Ex. Ionic compounds of tin & oxygen are SnO & SnO2

Bismuth Only has +3 charge Bi3+

50


Ions of Some Transition Metals & Post-transition Metals

51


Compounds with Polyatomic IonsBinary compounds

Compounds formed from 2 different elements

Polyatomic ions Ions composed of 2 or more atoms linked by

molecular bonds If ions are negative, they have too many

electrons If ions are positive, they have too few electrons

Formulas for ionic compounds containing polyatomic ions Follow same rules as ionic compounds Polyatomic ions are expressed in parentheses

52


53

Table 3.4 Polyatomic Ions

(Alternate Name in parentheses)


Learning CheckEx. What is the formula of the ionic

compound formed between ammonium and phosphate ions? Ammonium = NH4

+

Phosphate = PO43–

Ex. Between strontium ion and nitrate ion? Strontium = Sr2+ Nitrate = NO3

2–

54

(NH4)+ (PO4)3–

(NH4)3PO4

Sr2+ (NO3)– Sr(NO3)2


Nomenclature (Naming) IUPAC system to standardize name of

chemical compounds One system so that anyone can

reconstruct formula from name We will look at naming Ionic Compounds of

Representative metals Transition metals Monatomic ions Polyatomic ions Hydrates

55


56

Cations: Metal that forms only 1 positive ion

Cation name = English name for metal Na+ sodium Ca2+ calcium

Metal that forms more than 1 positive ion Use Stock System

Cation name = English name followed by numerical value of charge written as Roman numeral in parentheses (no spaces)

Transition metal Cr2+ chromium(II) Cr3+ chromium(III)

Naming Ionic Compounds


57

Anions: Monatomic anions named by adding

“–ide” suffix to stem name for element

Polyatomic ions use names in Table 3.5

Naming Ionic Compounds


58

Learning Check: Name The Following

K2O

NH4ClO3

Mg(C2H3O2)2

Cr2O3

ZnBr2

potassium oxide

ammonium chlorate

magnesium acetate

chromium(III) oxide

zinc bromide


59

Learning Check: Determine The Formula

Calcium hydroxide Ca(OH)2

Manganese(II) bromide MnBr2

Ammonium phosphate (NH4)3PO4

Mercury(I) nitride (Hg2)3N2


Your Turn!

Which is the correct name for Cu2S?

A. copper sulfide B. copper(II) sulfideC. copper(II) sulfate

D. copper(I) sulfide E. copper(I) sulfite


Your Turn!Which is the correct formula for ammonium sulfite?

a) NH4SO3

b) (NH4)2SO3

c) (NH4)2SO4

d) NH4S

e) (NH4)2S

61


Naming Hydrates Ionic compounds

Crystals contain water molecules Fixed proportions relative to ionic substance

Naming Name ionic compound Give number of water molecules in formula

using Greek prefixes

62

mono- = 1 hexa- = 6

di- = 2 hepta-

= 7

tri- = 3 octa- = 8

tetra- = 4 nona- = 9

penta-

= 5 deca- = 10


Learning Check: Naming Hydrates CaSO4 · 2H2O

calcium sulfate dihydrate CoCl2 · 6H2O

cobalt(II) chloride hexahydrate FeI3 · 3H2O

iron(III) iodide trihydrate

63


Your Turn!What is the correct formula for copper(II) sulfate pentahydrate?

A.CuSO4 · 6H2O

B.CuSO3 · 5H2O

C.CoSO4 · 4H2O

D.CoSO3 · 5H2O

E.CuSO4 · 5H2O

64


Molecular CompoundsMolecules

Electrically neutral particle Consists of two or more atoms

Chemical bonds Attractions that hold atoms together in

molecules Arise from sharing electrons between 2 atoms Group of atoms that make up molecule

behave as single particle

Molecular formulas Describe composition of molecule Specify # of each type of atom present 65


Molecules vs. Ionic CompoundsMolecules

Discrete unit Water = 2 hydrogen atoms bonded to 1 oxygen

atom

Ionic Compounds Ions packed as close as possible to each other

Sodium chloride =Each cation has 6 anions; each anion has 6 cations

No one ion “belongs” to another

66


Molecular Compounds Formed when nonmetals combine

C + O2 CO2 2H2 + O2 2H2O

Millions of compounds can form from a few non-metals

Organic chemistry & Biochemistry Deal with chemistry of carbon + H, N & O

A few compounds have only 2 atoms Diatomics: H2, O2, Cl2, HF, NO

Most molecules are far more complex Sucrose (C12H22O11) urea (CON2H4)

67


Hydrogen-containing CompoundsNonmetal hydrides

Molecule containing nonmetal + hydrogen Number of hydrogens that combine with

nonmetal = number of spaces from nonmetal to noble gas in periodic table

68

N O F Ne


3-D Shapes of Molecules Space filling models

Used to give shapes of simple nonmetal hydrides

Blue = nitrogen Red = water Yellow = fluorine White = hydrogen

69


Organic Compounds Carbon compounds

Carbon + hydrogen, oxygen, & nitrogen

Originally thought these compounds only came from living organisms Now more general

Hydrocarbons Simplest organic compounds Contain only C & H Always have ratio of atoms CnH2n+2

Named using prefix designating number of C atoms

All have –ane suffix70


Table

3.8

Hydrocarbons Belonging to the Alkane Series

71


Alkanes Boiling point increases as number of

carbon atoms increases Space filling models of alkanes

Black = carbon White = hydrogen

72


Your Turn!

Which is the correct name for C4H10?

A. methane B. ethane C. propane D. pentane E. butane


Other HydrocarbonsAlkenes

Hydrocarbons with two less H’s than alkanes CnH2n

Name = number prefix + ene

Ex. C2H4 = ethene (ethylene)

Alkynes Hydrocarbons with four fewer H’s than alkanes CnH2n – 2

Name = number prefix + ene

Ex. C2H2 = ethyne (acetylene)74


75

Other Organic Compounds Hydrocarbons are basic building

blocks of organic chemistry Many other classes of

compounds derived from

them

Alcohols Replace H in alkane with -OH group Name = number prefix + anol

Ex. CH3OH = methanol (methyl alcohol)

C2H5OH = ethanol (ethyl alcohol)


Your Turn!

What is the name of C4H9OH?

A. hexanolB. propanol C. pentanol D.tetranol E. butanol


Writing Formulas for Organic CompoundsMolecular formula

Indicates # of each type of atom in moleculeEx. C2H6 for ethane or C3H8 for propane Order of atoms

Carbon | Hydrogen | Other atoms alphabetically

Ex. sucrose is C12H22O11

Emphasize alcohol – write OH group last C2H5OH

Structural formula Indicate how carbon atoms are connected Ethane = CH3CH3

Propane = CH3CH2CH377


Your Turn!Octane is a hydrocarbon with 8 C atoms that is the major component of gasoline. What is the correct molecular formula for octane?

A.C8H14

B.C8H16

C.C8H18

D.C8H17OH

E.C8H15OH

78


Your Turn!What is the correct structural formula for octane?

a)CH3CH2CH2CH2CH2CH2CH2CH3

b)CH3CH2CH2CH2CH2CH2CH3

c)C8H18

d)CH3CH2CH2CH2CH2CH2CH2CH2CH3

e)CH3CH2CH2CH2CH2CH2CH2CH2OH

79


Nomenclature of Molecular Compounds Goal is a name that translates clearly into

molecular formula

Naming Binary Molecular Compounds Which 2 elements present? How many of each?

Format: First element in formula

Use English name Second element

Use stem & append suffix –ide Use Greek number prefixes to specify how

many atoms of each element 80


Naming Binary Molecular Compounds1. hydrogen chloride

2. phosphorous pentachloride

3. triselenium dinitride

Mono always omitted on 1st element Often omitted on 2nd element unless more

than one combination of same 2 elementsEx. Carbon monoxide CO Carbon dioxide CO2

When prefix ends in vowel similar to start of element name, drop prefix vowel

81

1 H 1 Cl HCl

1 P 5Cl PCl5

3 Se 2N Se3N2


82

Learning Check: Name EachFormat:

Number prefix + 1st element name Number prefix + stem + –ide for 2nd

element

AsF3 =

HBr = N2O4 =

N2O5 =

CO = CO2 =

arsenic trifluoride

hydrogen bromide

dinitrogen tetroxide

dinitrogen pentoxide

carbon monoxide

carbon dioxide


Your Turn!

Which is the correct formula for nitrogen triiodide?

A.N3I

B.NI3

C.NIO3

D.N(IO3)3

E.none of the above


Your Turn!

Which is the correct name for P4O10?

A. phosphorus oxide B. phosphorous decoxideC. tetraphosphorus decoxideD. tetraphosphorus oxideE. decoxygen tetraphosphide


Exceptions to Naming Binary MoleculesBinary compounds of nonmetals +

hydrogen No prefixes to be used Get number of hydrogens for each nonmetal

from periodic table Hydrogen sulfide = H2S

Hydrogen telluride = H2Te

Molecules with Common Names Some molecules have names that predate IUPAC

systematic names

Water H2O ▪ Sucrose C12H22O11

Ammonia NH3 ▪ Phosphine PH385


Summary of Naming

86

chapter 3: elements, compounds, and the periodic table chemistry: the molecular nature of matter, 6e...

Documents

e jespersenbradyhyslop

electron e

molecular nature of

jespersenbradyhyslop

particles electrons

e discovery of proton

e discovery of neutron

e atomic structure electrons