Unit 2 TBT Terms

Nonpolar Covalent Bonds

formed between two nonmetals, electrons are shared evenly

Polar Covalent Bonds

formed between two nonmetals, electrons are shared unevenly

Ionic Bonds

formed between metal and nonmetal, electrons are transferred

δ-

on more electronegative atom

δ+

on less electronegative atom

bond energy/bond strength

the amount of energy required to break a bond

(high bond energy = strong covalent bonds)

triple bond

shortest and strongest

1 σ bond and 2 π bonds

double bond

1 σ bond and 1 π bond

single bond

longest and weakest

1 σ bond

lattice energy

the energy required to separate the ions in an ionic lattice

(high lattice energy = strong ionic bonds)

Ionic bonds are stronger when…

1)

2)

1) the magnitude of the charge is greater

2) the ion size is smaller

Properties of Ionic Solids

• High Melting Points

• Low Volatility (don’t evaporate easily)

• Poor Conductors as Solids, Good Conductors when Molten/Aqueous

• Soluble in Water

• Brittle (shatter)

Properties of Metallic Solids

• High Melting Points

• Good Conductors of Electricity

• Good Conductors of Heat

• Malleable (hammered into sheets)

• Ductile (pulled into wires)

Metallic Bonds

formed between metals, electrons are delocalized into a “sea of electrons”

Substitutional Alloys

atoms of one metal are replaced by atoms of another

both metals have similar atomic radii

Interstitial Alloys

atoms of one element fill the gaps between atoms of a metal

one of the elements has a much smaller atomic radius

What is needed for a substance to conduct electricity?

charged particles (ions, delocalized electrons, etc.) that are able to move freely and carry charge

resonance structures

different valid drawings of the same molecule that differ only in electron (bond) placement, not atom positions

Formal Charge

# of Valence Electrons an Atom Starts With - # of Electrons Touching the Atom

The most valid resonance structure will…

1) minimize formal charge

2) put negative formal charge on the more electronegative atom

Geometry: Linear

Bond Angle: 180^o

Hybridization: sp

Geometry: Trigonal Planar

Bond Angle: 120^o

Hybridization: sp²

Geometry: Bent

Bond Angle: less than 120^o

Hybridization: sp²

Geometry: Tetrahedral

Bond Angle: 109.5^o

Hybridization: sp³

Geometry: Trigonal Pyramidal

Bond Angle: less than 109.5^o

Hybridization: sp³

Geometry: Bent

Bond Angle: less than 109.5^o

Hybridization: sp³

Geometry: Trigonal Bipyramidal

Bond Angle: 120^o and 90^o

Geometry: Seesaw

Bond Angle: less than 120^o and 90^o

Geometry: T-Shaped

Bond Angle: less than 90^o

Geometry: Linear

Bond Angle: 180^o

Geometry: Octahedral

Bond Angle: 90^o

Geometry: Square Pyramidal

Bond Angle: less than 90^o

Geometry: Square Planar

Bond Angle: 90^o

Isomers

different substances with the same molecular formula but different arrangements of atoms

Sigma (σ) Bonds

head-on overlap of orbitals

stronger than pi (π) bonds

Pi (π) Bonds

side-by-side overlap of orbitals

weaker than sigma (σ) bonds

Polar Molecules

bond dipoles do not cancel out, resulting in a net dipole moment

usually have…

• asymmetric geometry,

• lone pairs on central atom, or

• different terminal atoms

Nonpolar Molecules

bond dipoles cancel out

usually have…

• symmetric geometry,

• no lone pairs on central atom, and

• identical terminal atoms