Types of Chemical Bonds (what holds atoms together): Covalent – sharing electrons between non metal atoms to form molecules. Nonpolar – equal sharing.

BONDINGBOND TYPES

BOND ENERGIES

Types of Chemical Bonds (what holds atoms together):

Covalent – sharing electrons between non metal atoms to form molecules.

Nonpolar – equal sharingPolar – unequal sharing

Ionic – giving or taking electrons between atoms to form compounds.

Metallic – a “sea of electrons” among metal atoms to form the metal solid.

IONIC COVALENTBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

e- are transferred from metal to nonmetal

high

yes (solution or liquid)

yes

e- are shared between two nonmetals

low

no

usually not

MeltingPoint

crystal lattice true molecules

Types of Bonds

Physical State solid liquid or gas

odorous

“electron sea”

METALLICBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

MeltingPoint

Physical State

e- are delocalized among metal atoms

very high

yes (any form)

no

malleable, ductile, lustrous

solid

Ionic Bonding - Crystal Lattice

Types of Bonds

Covalent Bonding - True Molecules

Types of Bonds

Diatomic Molecule

Metallic Bonding - “Electron Sea”

Types of Bonds

CHEMICAL FORMULA

MolecularFormula

FormulaUnit

IONIC COVALENT

CO2NaCl

Chemical Bond

attractive force between atoms or ions that binds them together as a unit

bonds form in order to…○decrease potential energy (PE)○ increase stability

Bond Polarity Most bonds are a

blend of ionic and covalent characteristics.

Difference in electronegativity determines bond type.

Bond Polarity

ElectronegativityAttraction an atom has for a shared pair of

electrons.higher e-neg atom -

lower e-neg atom +

Bond Polarity Electronegativity Trend

Increases up and to the right.

Nonpolar Covalent Bonde- are shared equallysymmetrical e- densityusually identical atoms

Bond Polarity

+ -

Bond Polarity

Polar Covalent Bonde- are shared unequallyasymmetrical e- densityresults in partial charges (dipole)

Nonpolar (Pure)

Polar

Ionic

View Bonding Animations.

Bond Polarity

Bond Polarity

Examples:

Cl2

HCl

NaCl

3.0-3.0=0.0Nonpolar

3.0-2.1=0.9Polar

3.0-0.9=2.1Ionic

MOLECULAR POLARITY

When does a MOLECULE become polar??

Write some examples:

ATTRACTIONS BETWEEN ATOMS

INTRAMOLECULAR FORCESCovalent BondsIonic (Electrostatic) BondsMetallic Bonds

Examples:

8.4 in TEXTBOOK:Attractions between Molecules INTERMOLECULAR FORCES

Van der Waals Forces – weakest attractions○ Result of dipole interactions – when one polar

molecule “lines up” to another molecule○ Dispersion forces – occur between ALL molecules

(polar or not) and are momentaryHydrogen Bonds – strongest type of intermolecular

force○ Always involves hydrogen○ An attraction to a hydrogen atom ALREADY bonded

to another strongly electronegative atom○ Hydrogen becomes strongly polarized with a bond

and will therefore try to compensate when close to another molecule

BOND ENERGIES

Energy of Bonding

Endothermic – heat is a reactant heat is absorbed breaking a bond

Reaction 1(endo):

CD + 100kJ C + D

Energy of BondingExothermic – heat is a product heat is released making a bond less potential energy bond is more stable

Reaction 2 (exo): A + B AB + 100kJ

Reaction 3: E + B EB + 100kJ

Reaction 4: F + G FG + 400kJ

Reaction 1(endo): CD + 100kJ C + D

Reaction 2 (exo): A + B AB + 100kJ

Reaction 3: E + B EB + 100kJ

Reaction 4: F + G FG + 400kJ

Which bond is more stable, EB or FG?FG, because it takes more energy (300kj more) to break the bond

than EB.

Energy of Bond Formation

Bond EnergyShort bond = high bond energy