AP Chemistry Unit 2 Review

Hopefully I won't bomb this next test like I did the first

Ionic bond

A bond between a metal and nonmetal in which the metal loses an electron and the nonmetals gains one.

Avg. EN: Medium (one high, one low)

Difference in EN: Large

Covalent/Molecular Bond

A bond between nonmetals in which atoms share electrons to fill their valence shells; they all “grab” electrons

Avg. EN: High

Difference in EN: Small (lower if nonpolar, medium if polar)

Metallic bonds

A bond between metals in which metallic cations (positive ions) are attracted to a sea of electrons

Avg. EN: Low (metals want to lose electrons)

Difference in EN: Small

Electronegativity

A quantitative value used to measure the ability/desire of an atom to attract electrons to itself

Bond Polarity

Polar = electrons are shared unequally.

The more unequal the EN, the more polar a bond is.

Dipole Moment

The bigger the dipole moment, the more polar a bond is.

Intramolecular Forces

There are two main forces within a molecule:

1. 2 nuclei repel each other, 2 electrons repel each other

2. Nuclei + electrons attract each other

Bond Types

Single: 1 pair (2 electrons)

Double: 2 pairs (4 electrons)

Triple: 3 pairs (6 electrons)

Potential Energy

When there is little distance between atoms, there is a strong force of repulsion between the two, pushing them apart. When they reach a certain distance, called a “goldilocks zone,” there is a perfect amount of attraction between them. If they go too far apart, however, there will be no more attraction or repulsion between them.

Enthalpy

The average change in energy when a bond is broken- calculated by subtracting the total bond energy of the resulting bond from the energy from the starting bonds.

Lattice Energy

The energy required to separate 1 mol of solids into gaseous ions (similar to enthalpy, but for lattices)

Factors that determine Lattice Energy

(In order)

1. Ion Charge: More positive/negative = stronger attraction = more lattice energy

2. Ion Radius (size): Smaller = fewer energy levels = stronger Coulombic attraction = more lattice energy

Higher lattice energy means…

…harder, higher melting point, less soluble (prone to being dissolved) in water

Electron Removed From Metal

Ionization Energy

Electron Added to Nonmetal

Electron Affinity/Electronegativity

Ions Attract Each Other & Form Lattice

Opposite of lattice energy

Metal Characteristics

Easily molded, electrically conductive

Alloy

A material that contains multiple elements and has the characteristic properties of metals (examples: stainless steel, brass, etc.)

Substitution Alloy

The solute (what’s being dissolved) takes positions normally occupied by a solvent (what causes the dissolving)

Interstitial Alloy

Solute (what’s being dissolved) takes position in the holes between solvent (what causes the dissolving) atoms

Resonance

Structures with different electron arrangements

Isomers

Structures with different atom arrangements

Formal Charge

The original number of valence electrons subtracted by the amount of unbonded electrons subtracted by half of the shared electrons

Dominant Structure

When formal charges are closest to zero OR when negative formal charge is on a more electronegative atom

Traits of Delocalized Double Bonds

1. Extra stability

2. Between single bond & double bond in terms of length and strength

3. The more places delocalized, the closer it is to a single bond

Electron Domain

A group of electrons doing one “thing-” bonding or a lone pair (on the central atom)

Electron Geometry

The 3D spatial arrangement of electron pairs around a central atom so that they are as far away from each other as possible.

Molecular Geometry

The three-dimensional arrangement of atoms in a molecule.

2 domains

Name: Linear

Angle measure: 180º

Hybridization: sp

3 domains

Name: Trigonal Planar

Angle measure: 120º

Hybridization: sp²

4 domains

Name: Tetrahedron

Angle measure: 109.5º

Hybridization: sp³

5 domains

Name: Trigonal Bipyramid

Angle measure: 90º AND 120º

Hybridization: sp³d

6 domains

Name: Octahedron

Angle measure: 90º

Hybridization: sp³d²

Traits of Polar Molecules

• Some bonds must be polar

• Its shape must be assymetrical

Sigma Bonds

Literally ANY bond. All bonds are sigma

Sigma Pi Bonds

Double Bonds

Sigma Pi Pi Bonds

Triple Bonds