Chapter 9 - Periodic properties of the elements

The three QN (n, L, ML)

together describe the probability of finding one electron in a certain volume around the nucleus

Hund’s rule

when filling degenerate orbitals, each orbital holds only one electron as long as possible, and the electrons will have parallel spins

Pauli exclusion principle

individual orbitals hold a maximum of two electrons (with either up (+1/2) spins or down (-1/2) spins)

Condensed Electron Configuration (CEC)

abbreviation of previous noble gas to make a core. (ex: CEC Na = [Ne] 3s1)

Valence electrons

any electron out of the core (also equal to what group the element is in, 5A, 3B, etc.)

Cations in Electron configurations for A groups

electrons added last are removed first

Cations in Electron configurations for B groups

electrons in the s orbital are removed first

Anions in Electron configurations

the added electrons fill in the order predicted by the Aufbau principle

Nuclear charge

atomic number (z = # of protons)

The effective Nuclear charge (Zeff)

the nuclear charge (Z) - the charge shielded by other electrons (S) (equal to the # of valence electrons)

the radius of an atom

the distance from the center to the outermost shell

Ionic size

• Cation is smaller than neutral (less e-)

• Anion is larger than neutral (more e-)

Isoelectronic species

elements (Na+1, Mg+2, F-1, etc.) that have the same number of e-

Paramagnetic

unpaired electrons generate a magnetic field due to spin (S = absolute value of total.(unpaired e-) Ms)

Diamagnetic

Atom or ion with all paired electrons

Ionization energy (IE)

energy needed to remove an electron from an atom

Electron Affinity (EA)

the energy released (or absorbed) when an atom in the gas phase accepts one electron (X (g) + 1e- → X- (g)

Exothermic

EA < 0 (energy is released)

Endothermic

EA > 0 (energy is supplied)