ap chem unit 1

Atomic Structure

The arrangement and number of particles in an atom, including protons, neutrons, and electrons.

Periodic Table

A tabular arrangement of the chemical elements, organized by increasing atomic number and grouped by similar properties.

Mass number

The total number of protons and neutrons in an atomic nucleus.

Isotopes

Atoms of the same element that contain different numbers of neutrons.

Average atomic mass

The weighted average of the mass of an element's isotopes based on their relative abundance.

Moles (PV = nRT)

A calculation used in chemistry to relate the pressure, volume, temperature, and number of moles of a gas.

Avogadro’s number

6.022 x 10^23, the number of atoms or molecules in one mole of a substance.

STP

Standard temperature and pressure; defined as 1 atm and 273K.

Molarity

The concentration of a solution expressed as moles of solute per liter of solution.

Percent composition

The percentage by mass of each element in a compound.

Empirical formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular formula

The actual number of atoms of each element in a molecule of a compound.

Coulomb’s law

Describes the electrostatic force between two charged particles, given by F = kq1q2/(r^2).

Photoelectron spectroscopy

A technique that measures the energy of electrons emitted from atoms when they absorb electromagnetic radiation.

Electron configuration

The distribution of electrons among the various orbitals in an atom.

Aufbau principle

The rule that electrons occupy the lowest energy orbitals first.

Pauli exclusion principle

No two electrons in the same orbital can have the same spin.

Hund’s rule

Electrons will fill unoccupied orbitals before they pair up.

Ionization energy

The amount of energy required to remove an electron from an atom.

Electronegativity

A measure of how strongly an atom's nucleus attracts electrons in a bond.

Electron affinity

The energy change when an electron is added to a neutral atom in the gas phase.