CHEM 241 Need to Know

valence shell

outermost electron shell

valence electron

electron that occupies valence shell

electron shells (from smallest/inner to biggest/outer)

K, L, M, N

valence bond

number of bonds formed using valence electrons

periodic table “group”

represents number of valence electrons in atom

periodic table “period”

represents number of electron shells

electronegativity

elements (protons) power to pull electrons

induction

elements (protons) power to pull electrons through a bond

polarity

elements ability to distribute electrons unevenly

orbitals:

space where electrons occupy

sp3

tetrahedral

steric #: 4

109 bond angle
25% S-character

sp2

trigonal planar

steric #: 3

120 bond angle

33% S-character

sp

linear

steric #: 2

180 bond angle

50% S-character

octet rule

maximum 8 electrons in valence shell

covalent bond

sharing a pair of electrons between atoms

Formal charge

difference from valence electrons - charge on an atom

bronsted acid

proton donor (ex - HCl)

bronsted base

proton acceptor (ex - anything w/o a proton really)

lewis acid

electron acceptor (ex - BF3)

lewis base

electron donor

H-

hydride (2e-)

H

hydrogen atom (1e-)

H+

proton (0e-)

sigma bond

represents a single bond formed by head on overlap of atomic orbitals

pi bond

represents double or triple bonds formed by side ways overlap of p orbitals

VSEPR theory

electrons repulse each other to adapt a specific geometry

steric number

predicts geometry of molecule - # of atoms bonded + total # of lp

valence bond theory

two atomic orbitals overlap to share electrons

molecular orbital theory

when atomic orbitals overlap, one bonding MO and one anti-bonding MO are generated

localized lp

doesn’t occupy a p orbital - doesn’t participate in resonance

delocalized lp

occupies p orbital - participates in resonance

vinylic position

sp2 hybride position (right next to a carbon double bond)

allylic position

next to vinylic

resonance

represents pi electrons adequately

first resonance pattern

an allylic lp next to a pi bind

second resonance pattern

lp next to a C+

third resonance pattern

pi bond next to a C+ (allylic C+)

fourth resonance pattern

pi bond between two atoms with different electronegativity

fifth resonance pattern

alternating pi bonds in a ring

first rule for finding major resonance structure

must complete/fill octet, can’t exceed

second rule for finding major resonance structure

aim for neutral formal charge or the least amount of charges possible

third rule for finding major resonance structure

negative charges should be on more EN atoms, positive charges should be on less EN atoms

acid-base

the more stable the CB, the stronger the acid

first factor stabilizing CB (ARIO)

atoms in the same period are more stable if they’re more EN, and atoms in the same group are more stable if they’re bigger (gets bigger further down vertically)

second factor stabilizing CB (ARIO)

more resonance structure options means more stability

third factor stabilizing CB (ARIO)

more induction groups (more atoms with high EN that will pull electrons towards them), the more stable

fourth factor stabilizing CB (ARIO)

smaller orbital is more stable because electrons are closer to nucleus

most stable (sp > sp2 > sp3) least stable

curved arrow tail

electron rich - where e starts out from

curved arrow head

electron poor - where the e ends up going