UCLA Chem 30A Final

principal energy levels (shells)

regions of space that electrons are confined to

orbitals

the subshells that shells are divided into (given by s,p,d,f)

aufbau principle

Orbitals fill in order of increasing energy from lowest energy to highest energy

pauli exclusion principle

Only two electrons, with opposite spins, can occupy an orbital

hund’s rule

When orbitals of equal energy (degenerate) are available but there are not enough electrons to fill all of them, one electron is added to each orbital before a second electron is added to any one of them

valence shell

the outermost occupied electron shell of an atom

valence electrons

electrons in the valence shell of an atom; these electrons are used to form chemical bonds and in chemical reactions

lewis dot structure

the symbol of an element represents the nucleus and all inner shell

electrons; dots represent valence electrons

anion

gains electrons

cation

loses electrons

ionic solids

formed by the attraction of anions and cations

covalent bond

chemical bond formed by sharing electrons

polar covalent bonds

partially ionic or partially covalent bonds

electronegativity

a measure of an atom’s attraction for the electrons it shares with another atom in a chemical bond

pauling scale of electronegativity

- generally increases left to right in a row (period)

• generally increases bottom to top in a column (group)

Bond dipole moment

A measure of the polarity of a covalent bond

formal charge

the charge assigned to an atom in a molecule or a polyatomic ion (assuming bonding electrons are shared equally)

molecular dipole moment

the vector sum of the individual bond dipole moments in a molecule

• reported in debyes (D)