CHEM 121- Chapter 9

VSEPR model

valence shell electron pair repulsion model utilizes electron domains to determine 3D structure

Electron Domains- bonding

where there is a chemical bond (multiple bonds still count as one)

Electron Domains- non bonding

generated by lone pairs on the central electron

Electron domain geometry

total number of electron domains in a molecule orientations in 3D space

2 electron domains

linear model, bond angle- 180

3 electron domains

trigonal, bond angle- 120

4 electron domains

tetrahedral, bond angle- 109.5

5 electron domains

trigonal bipyramidal, bond angle- equatorial- 120, axial- 90

6 electron domains

octahedral, bond angle- 90

Molecular Geometry

accounts for the difference in size between the non bonding and bonding domains

AX2

Linear, bond angle - 180

AX3

trigonal planer, bond angle- 120

AX2E

bent, bond angle- <120

AX4

tetrahedral, bond angle- 109.5

AX3E

trigonal pyramidal, bond angle- <109.5

AX2E2

Bent, bond angle- «109.5

AX5

trigonal bipyramidal, equatorial bond angle- 120, axial bond angle- 90

AX4E

see saw, equatorial bond angle- <120, axial bond angle- <90

AX3E2

T shaped, bond angle- <90

AX2E3

linear, bond angle- 180

AX6

Octahedral, bond angle- 90

AX5E

square pyramidal, equatorial bond angle- 90, axial bond angle- <90

AX4E2

square planar, equatorial bond angel- 90

Bond polarity

measure of how equal an electron is shared in a covalent bond

non polar

electron is shared equally, x=0

polar

electron is shared unequally between the atoms, 0 < x < 2

electronegativity

ability to attract electrons towards itself

ionic

x> or = 2

Dipole moments

uneven distribution of electrons in a polar bond

Valence bond theory

lewis bonding + atomic orbitals, occurs when atomic orbitals overlap

hybrid orbitals

orbitals of different atoms will mix to make these things which dictate geometry, central atom makes the hybrid orbitals

sp

linear, bond angle- 180

sp2

trigonal planar, bond angle- 120

sp3

tetrahedral, bond angle- 109.5

single bond

1 sigma bond

double bond

1 sigma and 1 pi

triple bond

1 sigma and 2 pi

Molecular Orbital theory

describes electron behavior in molecules

Bond order

½ (bonding electrons(sigma or pi) - non bonding electrons(sigma*or pi*))

Bond order outcomes

0- no bond forms

1- single bond

2- double bond

3- triple bond