Chapter 4Chapter 4

The Structure of MatterThe Structure of Matter

How atoms form compoundsHow atoms form compounds

CompoundsCompounds Formed when two or more Formed when two or more

elements combineelements combine Must make a chemical changeMust make a chemical change New propertiesNew properties Atoms from the different elements Atoms from the different elements

form bondsform bonds Chemical Bond-Chemical Bond- the attractive the attractive

force that holds different atoms or force that holds different atoms or ions togetherions together

CompoundsCompounds Every compound has a specific Every compound has a specific

ratio of atomsratio of atoms Written as a chemical formulaWritten as a chemical formula HH22O, CO, C1212HH2222OO1212, NaCl, NaCl The ratio is the same every time, The ratio is the same every time,

every whereevery where Different ratio means a different Different ratio means a different

compoundcompound

Chemical StructureChemical Structure Shows how the atoms are Shows how the atoms are

arranged in the compoundarranged in the compound How the atoms or ions are How the atoms or ions are

connectedconnected In order to specify where we needIn order to specify where we need– Bond lengthBond length- distance between - distance between

the nucleithe nuclei– Bond angleBond angle- Angle between - Angle between

atoms (requires two bonds)atoms (requires two bonds)

ModelsModels Ball and stick- Ball represents Ball and stick- Ball represents

atoms, stick represents bondsatoms, stick represents bonds Easy to see bond anglesEasy to see bond angles Structural formulas- drawn with Structural formulas- drawn with

connections between atoms shown.connections between atoms shown.

HO

H

H

H

H

C O H

ModelsModels Space-filling – Shows that atoms Space-filling – Shows that atoms

the right size and in the right the right size and in the right place.place.

CC44HH99OO22NN

2 Types of structures2 Types of structures NetworksNetworks A large number of atoms, all A large number of atoms, all

bonded togetherbonded together Atoms bondedAtoms bonded Or ions opposite chargesOr ions opposite charges

Network SolidsNetwork Solids Many atoms all bonded togetherMany atoms all bonded together Quartz is SiOQuartz is SiO2 2

Major component of rocks.Major component of rocks. Each Silicon bonded to 4 oxygen atomsEach Silicon bonded to 4 oxygen atoms Angle is 109.5ºAngle is 109.5º Gives it a strong rigid Gives it a strong rigid

structurestructure Makes rocks hard.Makes rocks hard. Gives them a highGives them a high

melting and boiling pointmelting and boiling point

Network SolidsNetwork Solids Ions bond togetherIons bond together Opposite charges attractOpposite charges attract All the positives getAll the positives get

surrounded by negatives surrounded by negatives Get a repeatingGet a repeating

pattern pattern RigidRigid BrittleBrittle High mp and bpHigh mp and bp

MoleculesMolecules Specific atoms joined togetherSpecific atoms joined together Weaker attractions than ions.Weaker attractions than ions. Low melting and boiling pointsLow melting and boiling points Things we know as gases and Things we know as gases and

liquidsliquids Stronger attraction- higher melting Stronger attraction- higher melting

and boiling temperaturesand boiling temperatures

BondingBonding When the valence electrons When the valence electrons

interactinteract Atoms react to achieve full Atoms react to achieve full

outermost energy levelsoutermost energy levels Two ways to do thisTwo ways to do this– Share electronsShare electrons– Transfer electronsTransfer electrons

Keeping Track of ElectronsKeeping Track of Electrons Atoms in the same columnAtoms in the same column Have the same outer electron Have the same outer electron

configuration.configuration. Have the same valence electrons.Have the same valence electrons. Group 1 has 1 valence electronsGroup 1 has 1 valence electrons Group 2 has 2 valence electronsGroup 2 has 2 valence electrons Group 13 has 3 valence electronsGroup 13 has 3 valence electrons Group 14 has 4 valence electronsGroup 14 has 4 valence electrons etcetc

1 23 4 5 6 7

8Helium only has 2 valence electrons

Electron Dot diagramsElectron Dot diagrams A way of keeping track A way of keeping track

of valence electrons.of valence electrons. How to write themHow to write them Write the symbol.Write the symbol. Put one dot for each Put one dot for each

valence electronvalence electron Don’t pair up until Don’t pair up until

they have tothey have to

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons.

First we write the symbol.

NThen add 1 electron at a time to each side.Until they are forced to pair up.

Write the electron dot diagram Write the electron dot diagram forfor

NaNa MgMg CC OO FF NeNe HeHe

Electron Configurations for Electron Configurations for CationsCations

Metals lose electrons to fill their Metals lose electrons to fill their outer levelsouter levels

They make positive ions.They make positive ions.

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence Metals will have few valence electronselectrons

Ca

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence Metals will have few valence electronselectrons

These will come offThese will come off

Ca

Electron Dots For CationsElectron Dots For Cations

Ca+2

Metals will have few valence Metals will have few valence electronselectronsThese will come offThese will come offForming positive ionsForming positive ions

Electron Configurations for Electron Configurations for AnionsAnions

Nonmetals gain electrons to fill their Nonmetals gain electrons to fill their outer levelsouter levels

They make negative ions.They make negative ions.

Electron Dots For AnionsElectron Dots For Anions Nonmetals will have many Nonmetals will have many

valence .electrons.valence .electrons. They will gain electrons to fill outer shell.They will gain electrons to fill outer shell.

P P-3

Stable ArrangementsStable Arrangements All atoms react to fill their outer All atoms react to fill their outer

levelslevels Noble gases have full outer energy Noble gases have full outer energy

levels.levels. 8 valence electrons .8 valence electrons . Also called the octet rule.Also called the octet rule.

Ar

Ionic BondingIonic Bonding Anions and cations are held Anions and cations are held

together by opposite charges.together by opposite charges. The bond is formed through the The bond is formed through the

transfer of electrons.transfer of electrons. Electrons are transferred to fill Electrons are transferred to fill

their outer levelstheir outer levels

Ionic BondingIonic Bonding

Na Cl

Ionic BondingIonic Bonding

Na+ Cl-

Ionic BondingIonic Bonding All the electrons must be accounted for!All the electrons must be accounted for!

Ca P

Ionic BondingIonic Bonding

Ca P

Ionic BondingIonic Bonding

Ca+2 P

Ionic Bonding

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca

Ionic Bonding

Ca+2 P-3

Ca P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2P

-3

Ca+2

Ionic Bonding

Ca3P2

Formula Unit

Properties of Ionic CompoundsProperties of Ionic Compounds Crystalline structure.Crystalline structure. A regular repeating arrangement A regular repeating arrangement

of ions in the solid.of ions in the solid. Ions are strongly bonded.Ions are strongly bonded. Structure is rigid.Structure is rigid. High melting points- because of High melting points- because of

strong forces between ions.strong forces between ions.

Crystalline structureCrystalline structure

Do they Conduct?Do they Conduct? Conducting electricity is allowing Conducting electricity is allowing

charges to move.charges to move. In a solid, the ions are locked in place.In a solid, the ions are locked in place. Ionic solids are insulators.Ionic solids are insulators. When melted, the ions can move When melted, the ions can move

around.around. Melted ionic compounds conduct.Melted ionic compounds conduct. First get them to 800ºC.First get them to 800ºC. Dissolved in water they conduct.Dissolved in water they conduct.

Metallic BondsMetallic Bonds How atoms are held together in How atoms are held together in

the solid metalthe solid metal Metals hold onto there valence Metals hold onto there valence

electrons very weakly.electrons very weakly. Think of them as positive ions Think of them as positive ions

floating in a sea of electrons.floating in a sea of electrons.

Sea of ElectronsSea of Electrons

+ + + ++ + + +

+ + + +

Electrons are free to move through Electrons are free to move through the solid.the solid.

Metals conduct electricity.Metals conduct electricity.

Metals are MalleableMetals are Malleable Hammered into shape (bend).Hammered into shape (bend). Ductile - drawn into wires.Ductile - drawn into wires.

MalleableMalleable

+ + + ++ + + +

+ + + +

MalleableMalleable

+ + + +

+ + + ++ + + +

Electrons allow atoms to slide by.Electrons allow atoms to slide by.

Ionic solids are brittleIonic solids are brittle

+ - + -+- +-

+ - + -+- +-

Ionic solids are brittleIonic solids are brittle

+ - + -

+- +-+ - + -

+- +-

Strong Repulsion breaks crystal Strong Repulsion breaks crystal apart.apart.

Covalent bondsCovalent bonds Nonmetals hold onto their valence Nonmetals hold onto their valence

electrons.electrons. They can’t give away electrons to They can’t give away electrons to

bond.bond. Still want full outer levelStill want full outer level Get it by sharing valence electrons Get it by sharing valence electrons

with each other.with each other. By sharing both atoms get to count By sharing both atoms get to count

the electrons toward noble gas the electrons toward noble gas configuration.configuration.

Covalent bondingCovalent bonding Fluorine has seven valence Fluorine has seven valence

electronselectrons

F

Covalent bondingCovalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has seven

Covalent bondingCovalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons

Covalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons

Covalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons

Covalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons

Covalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electrons

Covalent bonding

F F

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level

Covalent bonding

F F8 Valence electrons

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level

Covalent bonding

F F8 Valence electrons

Fluorine has seven valence Fluorine has seven valence electronselectronsA second atom also has sevenA second atom also has sevenBy sharing electronsBy sharing electronsBoth end up with full energy levelBoth end up with full energy level

Single Covalent BondSingle Covalent Bond A sharing of two valence electrons.A sharing of two valence electrons. Only nonmetals and Only nonmetals and Hydrogen.Hydrogen. Different from an ionic bond Different from an ionic bond

because they actually form because they actually form molecules.molecules.

Two specific atoms are joined.Two specific atoms are joined. In an ionic solid you can’t tell In an ionic solid you can’t tell

which atom the electrons moved which atom the electrons moved from or to.from or to.

How to show how they formedHow to show how they formed It’s like a jigsaw puzzle.It’s like a jigsaw puzzle. I have to tell you what the final I have to tell you what the final

formula is.formula is. You put the pieces together to end You put the pieces together to end

up with the right formula.up with the right formula. For example- show how water is For example- show how water is

formed with covalent bonds.formed with covalent bonds.

WaterWater

H

O

Each hydrogen has 1 Each hydrogen has 1 valence electronvalence electron

Each hydrogen wants 1 Each hydrogen wants 1 moremore

The oxygen has 6 valence The oxygen has 6 valence electronselectrons

The oxygen wants 2 moreThe oxygen wants 2 more

They share to make each They share to make each other happyother happy

WaterWater Put the pieces togetherPut the pieces together The first hydrogen is happyThe first hydrogen is happy The oxygen still wants one moreThe oxygen still wants one more

H O

WaterWater The second hydrogen attachesThe second hydrogen attaches Every atom has full energy levelsEvery atom has full energy levels

H OH

Multiple BondsMultiple Bonds Sometimes atoms share more than Sometimes atoms share more than

one pair of valence electrons.one pair of valence electrons. A double bond is when atoms A double bond is when atoms

share two pair (4) of electrons.share two pair (4) of electrons. A triple bond is when atoms share A triple bond is when atoms share

three pair (6) of electrons.three pair (6) of electrons.

Carbon dioxideCarbon dioxide COCO22 - - Carbon is central Carbon is central

atomatom ( I have to tell you)( I have to tell you)

Carbon has 4 valence Carbon has 4 valence electronselectrons

Wants 4 moreWants 4 more Oxygen has 6 valence Oxygen has 6 valence

electronselectrons Wants 2 moreWants 2 more

O

C

Carbon dioxideCarbon dioxide Attaching 1 oxygen leaves the Attaching 1 oxygen leaves the

oxygen 1 short and the carbon 3 oxygen 1 short and the carbon 3 shortshort

OC

Carbon dioxide Attaching the second oxygen leaves

both oxygen 1 short and the carbon 2 short

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more

OCO

Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in

the bond

OCO

Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in

the bond

OCO8 valence electrons

Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in

the bond

OCO8 valence electrons

Carbon dioxide The only solution is to share more Requires two double bonds Each atom gets to count all the atoms in

the bond

OCO

8 valence electrons

Another way of indicating Another way of indicating bondsbonds

Often use a line to indicate a bondOften use a line to indicate a bond Called a structural formulaCalled a structural formula Each line is 2 valence electronsEach line is 2 valence electrons

H HO =H HO

Structural ExamplesStructural Examples

H C N

C OH

H

C has 8 C has 8 electrons electrons because each because each line is 2 line is 2 electronselectrons

Ditto for NDitto for N

Ditto for C hereDitto for C here Ditto for ODitto for O