CHEM 1170 EXAM 2

Frequency

 the number of wavelengths passing a certain point per second

What is the mnemonic for the waves?

Great Xylophones Use Vibrant Interesting Musical Rhythms

Photoelectric Effect

electrons are ejected from a metal in a vacuum by EM radiation

Bohr’s postulates on the H atom

1. An electron can only have specific energy values in an atom 

 2. An electron transitions from one energy level to another by the absorption or emission of a photon  

delta x =

 uncertainty in position 

delta Px

uncertainty in momentum 

n quantum #

principal

Energy level

1,2,3,…

l quantum number

angular momentum

l = 0, ... n-1

m quantum number

magnetic

• M = -l,...0,...+l

Ms

spin

• Ms= -½ , ½ 

Stern-Gerlach experiment

electron spin is quantized (Only spin up and down)

Pauli Exclusion Principle:

  No two electrons in an atom have the same four quantum numbers

Hund’s Rule-

When filling orbitals in the same sublevel, separate them with the same spin until it is necessary to pair them 

Paramagnetic -

 One or more unpaired electrons allows an atom to be affected by a magnetic field 

Diamagnetic

All electrons are spin paired. Unaffected by a magnetic field 

Atomic Radius 

Moving down a groUP atomic radius increases 

Moving from left to right in a period, radius decreases (skipping d block) 

Ionization Energy (I.E) -

 Energy to remove an electron from an atom 

Electron Affinity -

Energy involved in atom (or ion) accepting an e- 

Lattice Energy U -

The energy needed to change a solid ionic compound into ions in the gas phase (sublimation, dissociation)

Coordinate covalent bond

 both e- in the bond come from the same atom 

Electronegativity-

measure of ability of an atom in a bond to attract e- in that bond 

Formal charges of an atom

 (# of e-) - (# of nonbonding e-) - ½ (# of bonding electrons)