Bonding

Video 5.1Types of Bonds

Octet Rule Review

Atoms bond with other atoms by sharing or transferring electrons in order to achieve a stable octet (8 valence electrons). Bonding creates stability!

*When bonds are formed energy is ___________.

*When bonds are broken energy is ___________.

released

absorbed

Ionic BondsO Transfer of

electrons from the cation to the anion (metal to nonmetal).

O High melting point and boiling point

O Mostly hard crystalline solids

O Conduct as liquid (either melted or dissolved) due to mobile ions.

Ionic BondsSodium Chloride: NaCl (table salt) properties:O HardO Solid crystalsO High melting point,

forget boiling!O Liquid phase

conducts (electrolytes are salts)

Metallic BondsO Metals onlyO All metals lose their

valence electrons and form a sea of electrons

O High melting point and boiling point

O Insoluble in waterO Always able to conduct

heat and electric due to mobile electrons

O MalleableO Ductile

Metallic Bonds

Copper (Cu) properties:O Hard solidO High melting

point, forget boiling!

O Malleable and ductile

O ConductorO Can’t dissolve

Metallic BondsSea of electrons

Copper (I) ions Copper (II) ions

Covalent Bonds (Molecular)O Nonmetals onlyO Share electrons

between atomsO Low melting

point and boiling point

O Never conduct heat or electricity

O Soft solid or gas

Covalent Bonds

Dextrose C6H12O6

(Sugar) properties:O SoftO Melts easily in

sauce pans for caramel

O Doesn’t conduct (nonelectrolyte)

What type of bond is created?

1. Ca + O2. K + Br3. S + Cl4. I + S5. Li + Mg6. Ba + S

M+ NM = Ionic

NM + NM = Covalent

M + NM = Ionic

M + NM = Ionic

NM + NM = CovalentM + M = Metallic

Video 5.2Ionic Compounds

Review: Find the ionic formula:

1. K + Br

2. Mg + Cl

3. Na + S

4. Ca + S

KBr

MgCl2

Na2S

CaS

+ -

+2

-

+ -2

+2

-2

Draw Lewis structures:KBr

MgCl2

Na2S

CaS

Which subatomic particle is involved in bonding?

Electrons only!

Geometry of ionic crystals

Ions

Ionic crystal

Video 5.3Covalent Compounds

Covalent Lewis Structures Rules: CCl4

1. Add up all valence e-

2. Draw a skeletal structure with bonds between elements. Least frequent element in the middle.

3. Subtract 2e- from total for each bond drawn.

4. Draw in remaining e- to fill each atom’s octet.

5. Evaluate: each atom should have 8 e- only.

C: 4 + 4Cl: 7 = 32 valence e-

ClCl—C—Cl Cl

32-8=24

VSEPR

“Valence shell electron pair repulsion” is a model for molecules. Lone electron pairs are repelled by one another and should be placed as far apart as

possible.

Geometry1. Linear: The molecule is on one plane

(flat) such as CO2 or H2.

2. Bent: The molecule is bent at angle like H2O due to unshared electrons and two bonding pairs on the central atom.

Geometry3. Pyramidal: The molecule has a triangular

shape like NH3 due to a lone pair and three bonding pairs on the central atom.

4. Tetrahedral: The molecule has four bonding pairs and no lone pairs on

the central atom like CH4.

Examples:O Draw the following molecules and identify

their geometry:

1. PCl32. SiCl2H2

3. Br2

4. H2S

pyramidal

tetrahedrallinear

bent

Video 5.4Bond Polarity

Bond PolarityThe earth has two poles; North and South.

A magnet also has two poles.

Bonds may have two poles. This means one element is charged different than the other.

If a bond is polar, the two elements have different electronegativities. The element with a higher electronegativity will be more negative.

Bond Polarity

Bond Polarity

Nonpolar Bond

Bond PolarityElectronegativity

differenceBond type

0-0.4 Nonpolar

0.5-1.0 Polar

1.1-2.0 Very Polar

2.0-4.0 Ionic

Ionic, polar or nonpolar?1. C-Br2. Na-S3. C-C4. H-O5. K-O6. Be-B

7. As-O8. N-O9. C-O10.F-F11.S-C12.N-H

P

I

NP

P

I

I

P

P

P

NP

NP

P

Covalent BondingO If 2 atoms or more form a bond with the

same electronegativity the bonds are nonpolar and they share e- equally. ( F-F )

O If there is an electronegativity difference between bonded atoms, the bonds are polar and e- are pulled toward the more electronegative atom. (H-F)

O If a bond is polar, the molecule will have a slightly negative and slightly positive side, like 2 poles of a magnet.

Video 5.5Molecular Polarity

Molecular PolarityO A polar molecule

will be asymmetrical.

O A nonpolar molecule will have a symmetrical shape or all nonpolar bonds.

Molecular Polarity

Which are polar molecules? Show charges.

- - -

----

-

-

+++

+

++

NP P P

NP NP

Molecular Polarity

Water is polar, and like dissolves like, so only polar

molecules are soluble in water. Polar molecules are

also attracted to an electric field.

Molecular Polarity

O As you can see, normally polar molecules are unaligned.

O When a electric source comes by, the molecules quickly align themselves.

Video 5.6IMF

IMFO Intramolecular forces is another

name for bonds, that keep elements together in compounds.

O Intermolecular forces of attraction are weaker than bonds, but are responsible for holding a substance together (multiple molecules in a confined area).

IMF

O The stronger the IMF, the tighter the structure (solid). The melting and boiling points will be high.

O The weaker the IMF, the looser the structure (gas). The melting and boiling points will be low.

Dipole-DipoleO Dipole-Dipole attractions are strong

forces between polar molecules. It is like static holding the + and – charges together.

Hydrogen Bonding

A special case: Hydrogen Bonds are the strongest bonds between Hydrogen and very electronegative atoms such as F, O and N. (H bonds are FON!) For example, H2O and HF, due to their polarity, they will attract each other.

London Dispersion Forces (LDF)

The weakest attraction between nonpolar molecules occur because electrons temporarily shift creating a temporary + and – charge. The more electrons the compound has, the stronger the force is.

Summary

OFrom weak to strong:ONonpolar LDFOPolar Dipole Dipole forcesOHydrogen bondsOCovalent BondsO Ionic BondsOMetallic Bonds

Class Notes

Show the individual and bonded Lewis structures:

1. Li and F

2. Mg and O

3. Be and S

4. What did all the cations do? 5. What did all the anions do?6. Which of the subatomic particles were changed

and how were they changed?

Type of Bonding?1. CaCl22. CO2

3. H2O

4. BaSO4

5. K2O

6. NaF

7. Na2CO3

8. CH4

9. SO3

10.LiBr11.MgO12.NH4Cl

13.HCl

14.KI15.NaOH16.NO2

17.AlPO4

18.FeCl319.P2O5

20.N2O3