CHEM 20A - Midterm 2 (Lectures 11-21)

Ground State Electron Configuration

allowed and lowest energy, lower levels filled, parallel spin

Excited State Electron Configuration

allowed but at higher energy, lower levels NOT filled, NOT parallel spin, (violates Hund’s or Aufbau’s)

Forbidden Electron Configuration

not allowed (violates Pauli exclusion)

Column - changes in n (size of orbital)

going down a column → n inc, e are further away from nucleus

Row - Changes in effective nuclear charge

going to right → nuclear charge inc, more protons and neutrons, not good sheidling

atomic radius

distance of e from nucleus

atomic radius change

inc. down a group, inc left (bigger orbital, bigger atom)

electron affinity 

energy released when e is added 

electron affinity change

inc up, inc right, (stronger nuclear attraction, want e)

larger electron affinity

easier to add e (wants e)

smaller electron affinity

harder to add e (doesn’t want it)

ionization energy

energy required to move e

ionization energy change

inc up, inc right (same as electron affinity) (harder to remove e)

higher ionization

harder to remove e (want to keep e)

lower ionizaton

easier to remove e (want to give e away)

half filled subshell

extra stability, so hard to remove e 

valence electrons

number of e in orbitals of the highest n

core electrons

all other e

electronegativity

electron pulling power

ionic compound

diff in EN is greater than 2.0, e are NOT shared, (metal + nonmetal)

covalent compounds

diff in E is less than 2.0, e are shared (metal + metal)

anions

take e, negative (nonmetals)

cations

give e, positive (metals)

lattice energy

bond strength btw cations and anions

ionic radi __ as electrons inc

inc

ionic radi __ as protons inc

dec

lattice energy is bigger when ionic radi is __

smaller

Steps for Drawing Lewis Dot Structure

1) count total avail e

2) count total e needed

3) calcuate # of bonds ½ (e needed - e avail)

4) determine # of e remaining (e avail - 2 x bond number)

5) calculate formal charge (valence e - # of lone pair - # of bonds)

resonance structures

structures with same number of atoms but different arrangement of e

isomers

structures with diff arangements of atoms

elements with exapnded octect

elements below period 2

molecules with incomplete octet

B and Al

radicals

molecules with unpaired e, very reactive

internulcear PE - atoms are far apart

baseline, PE = 0

internulcear PE - moving closer

e are attracted by nucleus, attraction > repulsion, more stable, lower PE

internulcear PE - bond length

attraction = repulsion, PE is lowest

internulcear PE - too close

repulsion > attraction, less stable, higher PE

dissocation energy

energy needed to pull atoms apart/break bonds

bigger atomic radius mean __ bond length

longer

longer bond = length means ____ bond

weaker

all covalent bonds between different elements are

polar to some extent

only covalent bonds btw atoms of the same element are

nonpolar

VSPER Model

explains the shape of molecules

Valence Bond (VB) Theory

explains where e are in molecule

Molecular Orbital Theory (MO Theory)

explains the electron configuration of a molecule

steric #

number of bonds + number of lone pairs around the central atom 

lone pairs and double bonds

take up more space so angles are slightly smaller

the higher the electronegativity

the more polar the bond