chem 301 unit 2.2 yipeeee

time to be a #womeninstem successful chem nerd yessir

steps drawing lewis dot compunds

count total electrons

put surrounding atoms around central

fill surrounding electrons

put leftover on center as lone pairs

find formal charge when necessary

hypervalent molecule

more than octet rule, more than 8 electrons on central atom

formal charge

when the number of electrons does not equal the number of protons, a positive or negative charge will exist

how to assign formal charge

draw lewis structure

count num of electron in use around each atom in molecule (bond=1, lone pair is 2)

subtract inuse -num of valence

formal charge formula

fc= # e- valence — # e- inuse

formal charge of H

ZERO unless it is charged then it is whatever charge is

neutral molecule is __ stable

more

hypovalency

fewer than 8 electrons available

group 2a and 3a

hypervalency

atoms in n>= 3 (period 3), d orbitals can be involved

surround atoms should not have a

postive formal charge (when central has negative)

nobel gases are highly likely to be hypervalent

how to determine hyper valency

look at number of electrons around central atom and compare to number of unpaired electrons according to the periodic table, how many bonds they like to make vs how many atoms they need to bond with

radical

odd number of electrons

delocalization

sharing electrons across the molecule

resonance

describes a moleculr or ion that cannot be accurately represented by a single lewis structure but instead requires multiple interconnected resonance structures to depict the true arrangement of its delocalized electrons

preferred structure

one that doesnt show charges

resonance hybrid

a single more accurate representation of a molecules true structure, formed by combinig multiple resonance structures (called contributors)

what moves during resonance

only lone pairs and multiple bond

functional groups: heteroatom attached to carbon

alcohol, amine

alcohol

ROH

amine

R2N:H

functional groups: carbonyl derivatives

aldehyde, hetone, carboxylic acid, amide

aldehyde

RCHO

hetone

RC(O)R

carboxylic acid

RCO2H or RCOOH

amide

RCONHR

Steps to consider for best formal charge structure,

atoms in period 3 and below cannot be hypervalent/have expanded valance

Formal charge-1 should be on more electronegative atom (+1 on less)

in 3d representations straight line represents

in plane

in 3d representations wedged line represents

in front

in 3d representations dashed wedged line represents

behind

bond angle/line angle structure

using line with endpoints as carbons

lewis structures show

number of bonds (single, double, triple)

types of bonds (covalent, ionic)

but NOT shape of molecules

bond angle of tetrahedral

109.5

shape of molecule determined by

bond angles and lengths

bigger the atom, more shells it has,

more elongated bond

bonding and lone pairs are ____ for electronic geometry

equivalent, geometry based on number of e- rich regions around the central atom

how to predict electronic geometry

ABx

A

central atom

B

bonded pairs (atom sharing the bond)

x

numbers

AB(v2)

2 pairs

linear

180 degrees

AB(v3)

3 pairs

trigonal planar

120 degrees

AB(v4)

4 pairs

tetrahedral

109.5 degrees

(pyramid shape)

AB(v5)

5 pairs

trigonal bipyramidal

120 degrees

(sims diamond shape)

AB(v6)

6 pairs

octahedral

90 degrees

(square pyramid diamond)

VSEPR stands for

valence shell electron pair repulsion

vsepr theory

based on theory electron clouds repel each other

molecules adopt geometry to minimize these repulsive interactions

in vsper lone pair is

bigger than bonding pair

with vsepr lone pair will cause

compression- bond angle decreases and distortion occurs

1 lone pair distorted tetrahedral name

trigonal pyramidal

2 lone pair distorted tetrahedral name

bent

how to predict molecular geometry

ABxUx

U

unbonded lone pairs

AB2U1

bent

AB3U1

trigonal pyramidal

AB2U2

bent

AB4U1

seesaw

AB3U2

tshaped

AB2U3

linear (no distortion)

AB5U1

square pyramidal

AB4U2

square planar (no distortion)

no lone pair

molecular shape not distorted

bond dipole

dipole movement due to difference of electronegativity between two atoms sharing a bond

3 or more plane of symmetry

symmetrical

symmetrical

nonpolar

distortion/asymmetrical

polar

to be symmetrical

all surrounding must be same

no lone pairs (ACTUALLY NO DISTORTION remember two exceptions)

2 exceptions on distorition

AB2U3, AB4U2

dipole goes from

less en to more en

overall polarity can be determined by

adding indiv bond dipoles

hybridization

mixing orbitals from different subshells

sp3 shape

large lobe and tiny lobe

sp3 hybridzation

4 hybrid orbitals, combo of 1 s and 3 p (often single bond)

tetrahedral

sp3 hybridzation

3 hybrid orbitals, combo of 1 s and 2 p, one p stays unhybridized (often double bond)

trig planar

sp hybridization

2 hybrid orbitals, combo of 1 s and 1 p, two p orbitals stay unhybridized (often triple bond)

linear

sp3d hybridization

in hypervalency

5 hybrid orbitals, combo of 1 s and 3 p and 1 d

trigonal bipyramidal

sp3d2 hybridization

6 hybrid orbitals, combo of 1 s and 3 p and 2 d

octahedral

hybridization for a central atom in a structure in the valence bond method can be determined by

write lewis structure

predict electronic geometry

select hybridization to corresponding geometry

directions correspond to

num orbitals

covalent bonding

equilibrium between repulsive and attractive interactions

sigma bond formation

covalent single bond (overlap along same axis)

multiple bonds

pi bonds

pi bond formation

orthogonal overlap of unhybridized p orbitals

triple bond made of

1 sigma 2 pi

cant have pi wo

sigma

double and triple bonds count for

1 direction

resonance will not break

a sigma bond (only pi of double and triple