By Scott Becker
Updated Aug 30, 2022

Molecular shape can be predicted with the Valence Shell Electron Pair Repulsion (VSEPR) model, a foundational tool taught in advanced chemistry courses worldwide. VSEPR considers the number of bonding sites and lone pairs around a central atom to forecast a molecule’s geometry. A “bent” shape occurs when a central atom has two bonding sites and one or two lone pairs. By applying VSEPR principles, you can reliably determine whether a molecule adopts a bent configuration.

Step 1

Write down the chemical formula of the molecule (e.g., HF, NO).

Step 2

Calculate the total valence electrons using the periodic table. For guidance, refer to the Resources section on electron counting.

Step 3

Draw the Lewis structure: use single lines for bonds and dots for lone electrons. Remember that each bond contributes two electrons, and the total electrons in the structure must equal the count from Step 2.

Step 4

Identify the central atom and count its bonding sites plus lone electron pairs—this is the steric number.

Step 5

Analyze the steric number: a bent geometry requires a steric number of 3 or 4 with at least one lone pair. If the number differs, the molecule is not bent.

Step 6

Consult a VSEPR chart (see Resources) to match the steric number, bonding sites, and lone pairs to the predicted molecular shape.

TL;DR (Too Long; Didn’t Read)

When drawing the Lewis structure, if the electron count is off, adjust by adding double or triple bonds and removing lone pairs as needed to achieve a balanced structure.