Learn: VSEPR Theory: Molecular Shapes and Electron Pair Repulsions

AX₂ (2 bonds, 0 lone pairs)

Linear

AX₃ (3 bonds, 0 lone pairs)

Trigonal planar

AX₂E (2 bonds, 1 lone pair)

Bent

AX₄ (4 bonds, 0 lone pairs)

Tetrahedral

AX₃E (3 bonds, 1 lone pair)

Trigonal pyramidal

AX₂E₂ (2 bonds, 2 lone pairs)

Bent

AX₅ (5 bonds, 0 lone pairs)

Trigonal bipyramidal

AX₄E (4 bonds, 1 lone pair)

Seesaw

AX₃E₂ (3 bonds, 2 lone pairs)

T-shaped

AX₂E₃ (2 bonds, 3 lone pairs)

Linear

AX₆ (6 bonds, 0 lone pairs)

Octahedral

AX₅E (5 bonds, 1 lone pair)

Square pyramidal

AX₄E₂ (4 bonds, 2 lone pairs)

Square planar

Steric number formula

Steric number = (number of bonded atoms) + (lone pairs on central atom). A double or triple bond counts as ONE.

Order of repulsion strength

Lone pair-lone pair > lone pair-bond pair > bond pair-bond pair (lone pairs squeeze bond angles)

Where do lone pairs go in a trigonal bipyramid?

Equatorial positions (fewer 90° repulsions)

Where do 2 lone pairs go in an octahedron?

Opposite each other (trans) → square planar