Shapes of Chemical Bonding

VSEPR theory says electron groups spread out as far as possible. Count the groups around the central atom, subtract lone pairs, and the molecular shape falls out — along with the bond angle you'll be asked for.

Key Facts to Memorize

Linear

2 electron groups, 0 lone pairs, 180°. Examples: CO₂, HCN.

CO₂ — nonpolar, 2 double bonds (O=C=O)

HCN — polar, single C–H + triple C≡N

Electron groups: 2 electron groups, 0 lone pairs
Bond angle: 180°
Hybridization: sp
σ / π bonds: CO₂: 2 σ + 2 π · HCN: 2 σ + 2 π

Polarity: Nonpolar when both outer atoms are the same (CO₂ — the dipoles cancel); polar when they differ (HCN).

Trigonal planar

3 groups, 0 lone pairs, 120°. Examples: BF₃, CH₂O.

BF₃ — nonpolar, 3 single bonds

CH₂O — polar, 2 single C–H + 1 double C=O

Electron groups: 3 electron groups, 0 lone pairs
Bond angle: 120°
Hybridization: sp²
σ / π bonds: BF₃: 3 σ, 0 π · CH₂O: 3 σ + 1 π

Polarity: Nonpolar when all three outer atoms are identical (BF₃); polar when one differs (CH₂O).

Bent (from 3 groups)

3 groups, 1 lone pair, about 118°. Example: SO₂.

SO₂ — polar, 2 double bonds (resonance)

Electron groups: 3 electron groups, 1 lone pair
Bond angle: ≈118°
Hybridization: sp²
σ / π bonds: SO₂: 2 σ + 2 π (counting both resonance S=O bonds)

Polarity: Always polar — the lone pair breaks the symmetry, so the dipoles cannot cancel.

Tetrahedral

4 groups, 0 lone pairs, 109.5°. Examples: CH₄, CH₃Cl.

CH₄ — nonpolar, 4 single bonds

CH₃Cl — polar, 4 single bonds

Electron groups: 4 electron groups, 0 lone pairs
Bond angle: 109.5°
Hybridization: sp³
σ / π bonds: 4 σ, 0 π

Polarity: Nonpolar when all four outer atoms are identical (CH₄, CCl₄); polar as soon as one is different (CH₃Cl).

Trigonal pyramidal

4 groups, 1 lone pair, about 107°. Example: NH₃.

NH₃ — polar, 3 single bonds

Electron groups: 4 electron groups, 1 lone pair
Bond angle: ≈107°
Hybridization: sp³
σ / π bonds: 3 σ, 0 π

Polarity: Always polar — the lone pair sits on top, so the dipoles never cancel.

Bent (from 4 groups)

4 groups, 2 lone pairs, about 104.5°. Example: H₂O.

H₂O — polar, 2 single bonds

Electron groups: 4 electron groups, 2 lone pairs
Bond angle: ≈104.5°
Hybridization: sp³
σ / π bonds: 2 σ, 0 π

Polarity: Always polar — two lone pairs push the bonds down and create a strong net dipole.

Trigonal bipyramidal

5 groups, 0 lone pairs, 90° and 120°. Example: PCl₅.

PCl₅ — nonpolar, 5 single bonds

Electron groups: 5 electron groups, 0 lone pairs
Bond angle: 90° (axial) and 120° (equatorial)
Hybridization: sp³d
σ / π bonds: 5 σ, 0 π

Polarity: Nonpolar when all five outer atoms are identical (PCl₅); polar only if the different atoms are arranged so the dipoles do not cancel.

Octahedral

6 groups, 0 lone pairs, 90°. Examples: SF₆, SF₅Cl.

SF₆ — nonpolar, 6 single bonds

SF₅Cl — polar, 6 single bonds

Electron groups: 6 electron groups, 0 lone pairs
Bond angle: 90°
Hybridization: sp³d²
σ / π bonds: 6 σ, 0 π

Polarity: Nonpolar when all six outer atoms are identical (SF₆); polar when one is swapped out (SF₅Cl).

Al the Gator, the school mascot, wearing a lab coat with a blue D

Al says…

Draw the Lewis structure first, every single time. Shapes come from electron groups, and you can't count what you haven't drawn.

Practice This Topic

Flash Cards

Flip through every fact, shuffle, and repeat.

Practice Quiz

Ten questions, scored instantly. Regenerate for a fresh set.

Sample Problems

Worked examples with solutions you can hide.

External Tools

Blooket review game
Mrs. Cauthron's bonding shapes review set.
PhET: Molecule Shapes
Build molecules and watch the angles change.