Molecular Geometry

Valence Shell Electron Pair Repulsion Theory:  best arrangement of e- pairs is minimizing repulsion between them

e- pair geometry: arrangement of all e- pairs around cent. atom

molecular geometry: arrangement of atoms around cent. atom

**nonbonding e- have greater repulsive effect than bonding e-, bent angles in molecule

(bonding e- are attracted to 2 nuclei, nonbonding are attracted to only 1 nucleus)

Polarity

Atoms of elements do not always share e- equally

Polar molecule: one end of molecule is δ – and one end is δ +

Dipole: 2 electrical charges of = magnitude but opp. sign separated thru dist

μ = Q x r

μ = dipole moment (units: debyes D)

Q = charge

r = distance separating charges

1 D = 3.34 x 10^-30 C x m

e- charge = 1.60 x 10^-19 C

↑ Q  =  ↑ μ (r const)

↑r = ↑ μ (Q const)

Vector quantity: has magnitude and direction

Polarity depends on:

· dipole moment (Dif in electronegativity)

· Geometry of molecule

H₂O                 vs.        CO₂