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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
