Basic Molecular Shapes and VSEPR Theory

Tetrahedral

4 bonding pairs, no lone pairs.

Tetrahedral Bond Angle

109.5°

Tetrahedral Explanation

Electron pairs repel equally, forming a symmetrical shape with 4 bonds.

Trigonal Pyramidal

3 bonding pairs, 1 lone pair.

Trigonal Pyramidal Bond Angle

~107°

Trigonal Pyramidal Explanation

The lone pair repels more strongly than bonding pairs, slightly reducing bond angles.

Bent (4 electron domains)

2 bonding pairs, 2 lone pairs.

Bent (4 domains) Bond Angle

~104.5°

Bent (4 domains) Explanation

Lone pairs push bonding pairs closer together, decreasing bond angles.

Trigonal Planar

3 bonding pairs, no lone pairs.

Trigonal Planar Bond Angle

120°

Trigonal Planar Explanation

Bonding pairs repel equally in a flat, triangular shape.

Bent (3 electron domains)

2 bonding pairs, 1 lone pair.

Bent (3 domains) Bond Angle

<120°

Bent (3 domains) Explanation

The lone pair repels bonding pairs, bending the molecule and reducing angles.

Linear

2 bonding pairs, no lone pairs.

Linear Bond Angle

180°

Linear Explanation

Bonding pairs are as far apart as possible in a straight line.

Octahedral

6 bonding pairs, no lone pairs.

Octahedral Bond Angle

90°

Octahedral Explanation

Bonding pairs arrange symmetrically to minimize repulsion.

Square Pyramid

5 bonding pairs, 1 lone pair.

Square Pyramid Bond Angle

~90°

Square Pyramid Explanation

Lone pair pushes bonds slightly, distorting the octahedral shape.

Square Planar

4 bonding pairs, 2 lone pairs.

Square Planar Bond Angle

90°

Square Planar Explanation

Lone pairs arrange opposite each other, keeping the molecule flat.

Trigonal Bipyramidal

5 bonding pairs, no lone pairs.

Trigonal Bipyramidal Bond Angles

90° & 120°

Trigonal Bipyramidal Explanation

Three atoms form an equatorial triangle (120°), and two atoms align axially (90°).

See-Saw

4 bonding pairs, 1 lone pair.

See-Saw Bond Angles

<90° & <120°

See-Saw Explanation

The lone pair pushes bonds into an asymmetric shape.

T-Shaped

3 bonding pairs, 2 lone pairs.

T-Shaped Bond Angle

<90°

T-Shaped Explanation

Lone pairs occupy equatorial positions, forcing a T-like structure.

Linear (Expanded Octet)

2 bonding pairs, 3 lone pairs.

Linear (Expanded Octet) Bond Angle

180°

Linear (Expanded Octet) Explanation

Lone pairs occupy equatorial positions, keeping the bonding atoms in a straight line.

Hypovalent Atoms

B, Be, Al

Hypovalent Mnemonic

"Bery (Be) Bored (B) About Electrons" (These elements don't need 8).

Hypervalent Atoms

P, S, Xe, I, Cl (Can hold more than 8 valence electrons).

Hypervalent Mnemonic

"People Say Xenon Is Cool"