AP Chemistry Unit 2

Chemical bonds

hold atoms together. Bonding plays a central role in determining the course of chemical reactions. Water turning from a solid to a liquid is not a chemical reaction.

Ionic Bonds

bond with metals and nonmetals. The electronegativity difference is pretty big. Ionic bonds form between two atoms when there is an electron transfer from one atom to another.

Cation

positively charged ion

Anion

negatively charged ion

Ionic Bond Examples

Examples are NaCl and CaCO3

Ionic Solids Structure

have a crystal lattice structure: a highly ordered structure of ions. Ions are fixed and their position are not free-moving.

Physical Properties of Ionic Compounds

include rigidity and brittleness, as well as a high melting point. Poor conductor of electricity as a solid, but a good conductor of electricity in liquid and aqueous state. Ionic bonds are very strong, which is why they have high melting and boiling points.

Coulomb’s Law

The more charge on the objects means a stronger force, and a greater distance results in a weaker force, think of it like magnets. Opposite charges attract more while like charges repel.

Covalent Bond

forms between two nonmetals. They form when two atoms share electrons instead of one transferring electrons to another (ionic). Nonpolar covalent bonds mean that the electrons are shared equally. Polar covalent bonds occur when the atoms share electrons unequally.

Metallic Bonds

form between two metals, and cations as well.

Electronegativity

increases from left to right and down a column.

Single Bonds

when atoms share two electrons (longest and weakest bonds)

Double Bonds

When atoms share four electrons

Triple Bonds

When atoms share six electrons (the shortest bond and strongest bond out of the three)

Covalent Bonding

are basically an overlap of the electron cloud

Metals Properties

hard, solid, and shiny.

Metal Structure

consist of metallic cations and then delocalized electrons - electrons that are free to move. Cations are also arranged in a lattice structure. Metals are good conductors of electricity due to freely moving electrons

Metallic Bonding

are attractions between metallic cations and delocalized electrons.

Malleable and Ductile

Metals are malleable - create a thin sheet and ductile - stretch it to a thin wire.

Alloy

a mixture of different metals. Harder, stronger, and less malleable than pure metals.

Octet Rule

eight valence electrons for each element

Valence Electrons

To find the number of valence electrons, look at the column, and everything from Hydrogen to Helium goes in a 1-8 pattern.

Check Lewis Dot Diagram

To check the Lewis dot diagram, first check the total valence electrons, then check for the octet rule.

Finding Lewis Dot Structure

To find Lewis dot structure - 1. Find the total number of valence electrons in center 2. Put the least electronegative atom in the center (hydrogen always goes on the outside) 3. Put two electrons between atoms to form a chemical bond 4. Complete octets on the outside atoms. Step five. If the central atom does not have an octet, move electrons from outer atoms to form double or triple bonds.

Formal Charge Formula

number of valence electrons - number of lone pair electrons - number of bonding pair electrons divided by 2. Formal charges of 0 are always preferred.

Resonance Structures

multiple Lewis structures are used to represent a single molecule or ion when a single Lewis structure cannot adequately describe the distribution of its electrons.

Expanded Octet

An overfilled molecule, or an expanded octet, has a central atom that is bonded to more than eight valence electrons. This exception only occurs for non-metals in the third period and below, such as phosphorus, sulfur, and chlorine.

Incomplete Octet

has a central atom that is stable with fewer than eight valence electrons. This is most common for elements like boron and beryllium.

VSEPR

Valence Shell Electron Pair Repulsion: Predict molecular geometry by miniziming electron-electron repulsion.

Lewis Dot vs VSEPR

Lewis dot diagram IS NOT the same as VESPR

Hybridization

fusion of orbitals of different energy subshells to form new orbitals with the same energy level

Electron Pair

Electron pair includes lone pair plus the bonding pair electrons.