AP Chemistry Course Study Guide Unit 1: Atomic Structure and Properties

A comprehensive set of vocabulary flashcards based on the AP Chemistry course, covering essential terms related to atomic structure, periodic trends, bonding, and chemical reactions.

Avogadro's number

The number of particles in one mole of a pure substance, approximately $6.022 imes 10^{23}$.

Atomic mass unit (amu)

A unit of mass used to express atomic and molecular weights, defined as one twelfth of the mass of an unbound atom of carbon-12.

Mass spectrum

A chart that represents the mass-to-charge ratio of ions, used to determine isotopes and their relative abundances.

Law of definite proportions

The principle that in a given compound, the elements are always combined in fixed, definite proportions by mass.

Empirical formula

The simplest whole number ratio of elements in a compound.

Core electrons

Electrons that are found in the inner shells of an atom, not involved in chemical bonding.

Valence electrons

Electrons that are in the outermost shell of an atom, responsible for chemical bonds.

Aufbau Principle

The principle that states electrons fill the lowest energy orbitals first.

Hund's Rule

The principle that states that every orbital in a subshell is singly occupied before any orbital is doubly occupied.

Pauli Exclusion Principle

The principle that states that no two electrons in the same atom can have identical values for all four quantum numbers.

Photoelectron spectroscopy (PES)

A technique used to measure the energy levels of electrons in an atom by photon interaction.

Periodic trends

Patterns observed in the periodic table regarding atomic radius, ionization energy, electron affinity, and electronegativity.

Effective nuclear charge

The net positive charge experienced by valence electrons from the nucleus, affecting atomic size.

Ionization energy

The energy required to remove an electron from an atom.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons.

Electron affinity

The amount of energy released when an atom gains an electron, often represented as a negative value.

London dispersion forces (LDF)

Weak intermolecular forces arising from temporary dipoles in atoms and nonpolar molecules.

Dipole-dipole interactions

Attractive forces between the positive end of one polar molecule and the negative end of another.

Hydrogen bonding

A strong type of dipole-dipole interaction that occurs between a hydrogen atom and a highly electronegative atom (F, O, N).

Lattice energy

The energy required to separate one mole of an ionic solid into its gaseous ions.

Lewis structure

A diagram that shows the arrangement of valence electrons among atoms in a molecule.

VSEPR theory

Valence Shell Electron Pair Repulsion theory; it predicts the shape of molecules based on electron pair repulsions.

Hybridization

The mixing of atomic orbitals to form new hybrid orbitals for bonding.

Equilibrium constant (K)

A numerical value that expresses the ratio of products to reactants at equilibrium in a reversible reaction.

Gibbs Free Energy (ΔG)

The energy associated with a chemical reaction that can be used to do work, predicting the spontaneity of a reaction.

Enthalpy (ΔH)

The heat content of a system, used to measure the energy changes during a reaction.