Why do atoms form bonds? To attain a noble gas configuration. How do atoms form bonds? By gaining, losing, or sharing electrons. Gain or loss of electrons.

Why do atoms form bonds?Why do atoms form bonds?

To attain a noble gas configuration.

How do atoms form bonds?How do atoms form bonds?

By gaining, losing, or sharing electrons.

Gain or loss of electrons ionic bondingSharing of electrons Sharing of electrons covalent bonding covalent bonding

Covalent BondingCovalent Bonding

• Results from the attraction between the nucleus on one atom and the electrons on another atom.

The electrons are shared, but not transferred.

Often formed between 2 nonmetal atoms of the same element.

If Attractions are If Attractions are greater than greater than Repulsions, a Repulsions, a bond is formed.bond is formed.

Potential Energy vs. Internuclear DistancePotential Energy vs. Internuclear Distance

Low energy Low energy High stabilityHigh stabilityBonding SystemsBonding Systems

Non-Bonding Systems

Different ways of representing a Different ways of representing a covalent bond.covalent bond.

Compounds with covalent bonds Compounds with covalent bonds are molecular!are molecular!

Recognizing covalent formulasRecognizing covalent formulas

• Covalent bonding occurs between nonmetal atoms.

• Formulas contain nonmetals.

Identify Bond Type from FormulaIdentify Bond Type from Formula

CHCH44 CuCu SOSO22

NaClNaCl HH22OO CsFCsF

MgMg NaNa22SS LiLi33NN

COCO22 AgAg AuAu

CaBrCaBr22 AlAl22OO33 CHCH33OHOH

AlAl NN22OO55 ZnOZnO

CovalCoval

CovalCoval

CovalCoval

CovalCoval

CovalCoval

CovalCoval

IonicIonic

IonicIonic

IonicIonic

IonicIonic

IonicIonic

IonicIonic

IonicIonic

MetalMetal

MetalMetal

MetalMetal MetalMetal

MetalMetal

MMaking a bond aking a bond LLiberates energy!iberates energy!

Separate AtomsSeparate Atoms

MoleculeMolecule

A + B A + B AB + energy AB + energy

• A and B are both atoms

• AB is a molecule

• In this particular case, no bonds are broken and one bond is formed.

• Energy is released.

• The reaction is exothermic.

A + B A + B AB + energy AB + energy

• A bond is formed & energy is released.

• AB has less potential energy than A + B.

• AB is more stable than A + B

BBreaking a Bond reaking a Bond AAbbsorbs Energy!sorbs Energy!

CD + energy CD + energy C + D C + D

• CD is a molecule; C and D are atoms.

• One bond is broken; no bonds are formed.

• This reaction is endothermic.

• C and D have higher potential energy than CD.

Structure of Covalent CompoundsStructure of Covalent Compounds

• They form molecules.

• The more reactants you have, the more molecules you can make.

Representations of MoleculesRepresentations of Molecules

Space-filling modelSpace-filling model Ball-and-stick modelBall-and-stick model

Ball-and-stick Ball-and-stick and electron and electron cloudcloud

Representations of MoleculesRepresentations of Molecules

Lewis Structures of ReactionLewis Structures of Reaction

HH22 = Molecular Formula = Molecular Formula

H-H = Structural Formula. H-H = Structural Formula.

- Represents 1 pair of electrons.- Represents 1 pair of electrons.