The forces at work are: Electromagnetic: Repulsion of like charges: proton-proton and electron-electron Attraction of unlike charges: proton-electron. Magnetic: Electron spin introduces magnetic forces. Electrons with opposite spins produce opposite magnetic poles. Opposite magnetic poles attract. Opposite spin is required for electrons to occupy the same orbital.

The Energies involved: Electron (orbital) Potential Energy: 2s 2p 3s 3p 3d 4s 4p 1s ENERGY LEVEL

120 o o 90 o 180 o Bond Angles

PxPx PyPy PzPz PxPx PyPy PzPz

Methane building blocks

2s2p x 2p z 2p y 1s sp 3 sp o Promote Hybridize x z y Methane: Carbon

CH 2 O 120 o

2s2p x 2p z 2p y 1s sp 2 sp 2 sp o Hybridized Formaldehyde: Carbon Promoted 120 o Trigonal Planar 2s + 2p x + 2p z

2s2p x 2p z 2p y 1s sp 2 sp 2 sp o Hybridized Formaldehyde: Oxygen 120 o Trigonal Planar Lone Pairs 2s + 2p x + 2p z

Formaldehyde Sigma bond 2 Lone Pairs bond bond

2s2p x 2p z 2p y 1s sp Promoted Hybridized Hydrogen Cyanide: Carbon 2s + 2p x Linear

2s2p x 2p z 2p y 1s sp Hybridized Hydrogen Cyanide: Nitrogen 2s + 2p x Linear

bond bond

PCl 5

3s3p x 3p z 3p y 2 Neon 120 o Hybridized Phosphorus Pentachloride: Phosphorus Trigonal Bipyrimidal sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d d xz d yz d xy d x 2 -y 2 d z o 90 o Promoted