Chem 120 Formula Sheet: Midterm Exam #2
Ch5 – Electronic Structure
Avogadro’s # = 6.022 x 1023 things per mole
What’s Nu? (c over lambda !)
or c =  
c = 3.00 X 108 m/s
Planck’s Law: E = n h , Planck’s constant h = 6.63 X 10-34 J-s and n = # of photons
Rydberg Equation: 1 /  = R (1/ n12 - 1/ n22 )
R = 1.096776 x 107 m-1
Energy states for Hydrogen atom: E = -2.18 X 10-18 J (1/ n2 )
De Broglie Wavelength
 = h / mv
for matter waves
Heisenberg’s Uncertainty Principle x mv  h /4 for location and momentum
Schrodinger Wave Equation: quantum numbers  specific orbitals
n, l, ml , ms
(each electron has a unique set of quantum numbers)
orbitals: s - 1, p - 3, d - 5, f – 7
Hund’s rule: partially fill all before completing any
Pauli Exclusion Principle: spin quantum number must differ for electrons in same orbital
Ch6 – Periodic Properties
Effective nuclear charge = Z – S (inner shell electrons)
Cations are smaller than elements
Anions are larger than neutral elements
Atomic radius decreases across periods Left to right because of Z effective
Atomic radius increases down periods because of adding shells, n gets bigger
Electron symmetry decreases ionization energy (easier to ionize the second of a pair of
electrons in an orbital from repulsion
Electron affinities are negative, energy must be lost to put electrons on neutral atoms
Ch7 – Intro to Bonding
Formal charge = Valence of atom– half of bonding electrons+all non-bonding electrons)
More stable molecules have lower formal charges or contrasts between atoms
Dipole moment = μ = Qr , Q n x (1.60 x 10-19 C) and r in angstroms (10-10 m) for
calculating charge separation. The conversion is 1D=3.34 x 10-30 C-m. D= Debyes
Octet rule, stable molecules complete octets where possible.
Bonding pairs = total electrons in molecule/8
Non bonding pairs = remainder/2
Treat hydrogen as if it had 7 electrons all others use group numbers to total valence shell
electrons in a molecule.
Don’t for get to add or subtract charges for ions