High School Chemistry  ·  Practice by Skill

Lewis Structures and VSEPR Practice Problems

A Lewis structure is a picture of how a molecule's valence electrons are shared and held as lone pairs. From that picture you can predict the molecule's shape, whether it is polar, and how it sticks to other molecules. Practice below covers valence electron counts, Lewis structures, VSEPR shapes, polarity, and bond types.

What you’ll practice

  • Counting valence electrons: find the total electrons available before you draw anything.
  • Drawing Lewis structures: place bonds and lone pairs so every atom has a full outer shell.
  • VSEPR shapes: predict geometry from the number of bonding and lone pairs around the central atom.
  • Polarity and bond types: decide whether bonds and whole molecules are polar, and tell ionic from covalent bonding.

Learn the method first →

A quick example: water

Count valence electrons for H2O: 2(1) + 6 = 8.

Put oxygen in the center with a single bond to each hydrogen. That uses 4 electrons, and the other 4 become 2 lone pairs on oxygen.

Oxygen now has 4 electron groups: 2 bonds and 2 lone pairs. The lone pairs push the bonds closer together.

The shape is bent, and because the bond dipoles do not cancel, the molecule is polar.

3 free lewis structures and vsepr problems

Give each one a real try before you open the solution. Your answer is checked as soon as you submit it, and the worked solution shows every step so you can see exactly where a setup went wrong.

#1Valence Electrons
How many total valence electrons are in a molecule of phosphorus trichloride (PCl3)? (P has 5 valence electrons; Cl has 7 each.)
#2Bond Types
An ionic bond is best described as…
#3Molecular Polarity
Carbon tetrachloride (CCl4) has four polar C–Cl bonds (ΔEN ≈ 0.5). Yet CCl4 is a nonpolar molecule. Why?

Questions you might have about lewis structures and vsepr

How do I draw a Lewis structure?
Add up the valence electrons, connect the atoms with single bonds, then spread the remaining electrons as lone pairs, outer atoms first. If the central atom is short of an octet, turn lone pairs into double or triple bonds.
How do I predict molecular shape with VSEPR?
Count the electron groups around the central atom, because they spread out as far as possible. Then name the shape by the atoms only: 4 groups with 0 lone pairs is tetrahedral, with 1 lone pair is trigonal pyramidal, and with 2 is bent.
How can I tell if a molecule is polar?
First check whether the bonds are polar, using the difference in electronegativity. Then check the shape: if the bond dipoles cancel in a symmetric shape, as in CCl4, the molecule is nonpolar.
What is the difference between ionic and covalent bonds?
An ionic bond is the attraction between a positive and a negative ion after electrons transfer, usually from a metal to a nonmetal. A covalent bond is a pair of electrons shared between two nonmetal atoms.
High School Chemistry · Lewis Structures and VSEPR Practice Problems