Molecular Geometry

6.5

Hybridization

• Mixing of two or more atomic orbitals of similar E’s on the same atom to produce new hybrid atomic orbitals of = E• Hybrid orbitals = orbitals of = E

produced by the combination of 2 or more orbitals of the same atom

An Example• Methane (CH4) –All bonds b/t C and H are identical–C has a valence config of 2s2 2p2 (leaving 4

spaces for H to join)–In order for all 4 spaces to be =, the s and

p orbitals hybridize sp3

–__ __ __ __ sp3

VSEPR Theory

• Valence Shell Electron Pair Repulsion Theory – the shape of a molecule will be so that e-’s are as far apart as possible• Takes into account bonded atoms

and lone pairs of __________.

Determining Shapes

• Look at steric number (how many things are around central atom).• Look at lone e- pairs• Use the sheet to help you determine

geometry

Polarity• Uneven distribution of electrical

__________ in an atom• If one atom in a bond pulls e- better than

the other and that pull is not balanced out you have a polar molecule• CH4 balances b/c of shape = non polar

• NH3 does not balance b/c shape= polar

• Try determining polarity on LS sheet

Intermolecular Forces

• Vary in strength but are ___________ than bonds• Strongest IMF is b/t polar molecules• Dipole – created by equal but

opposite charges that are separated by a short distance

IMF

• Dipole-Dipole Forces – b/t polar molec.• A short range force b/t nearby molec.• Look at the b.p. of I-Cl and Br-Br.• I-Cl – is 97°C and Br-Br is 59°C• This is due to the _______-_________

force between ____ and _____

IMF

• Dipole-Dipole induced dipole – a nonpolar molecule becomes a slight dipole b/c a ___________ molecule attracts it’s electrons• Weaker than dipole-dipole

IMF

• Hydrogen Bonding – a H atom bonded to a highly e-neg atom is attracted to an unshared pair of e-’s of an e-neg atom in a nearby molec.• Quite strong responsible for

_______ b.p.’s of some materials (H2O)

• In dipoles

IMF

IMF

• London Dispersion Forces – results from the constant motion of e-’s and the creation of instantaneous dipoles• Between __________ polar

molecules