Enter the number of valence electrons, bonding electrons, and lone pair electrons into the calculator to determine the number of unpaired electrons. This calculator can also evaluate any of the variables given the others are known.

Unpaired Electrons Formula

The following formula is used to calculate the number of unpaired electrons in an atom.

UE = V - B - L

Variables:

  • UE is the number of unpaired electrons
  • V is the number of valence electrons in the atom
  • B is the number of bonding electrons
  • L is the number of lone pair electrons

To calculate the number of unpaired electrons, subtract the number of bonding electrons and the number of lone pair electrons from the total number of valence electrons in the atom.

What is a Unpaired Electrons?

Unpaired electrons refer to the electrons in an atom that do not pair up with another electron in an orbital. These electrons have the same spin quantum number, which means they spin in the same direction. They are often responsible for the magnetic and chemical properties of an atom, as they are more likely to be involved in chemical reactions. Unpaired electrons are typically found in atoms, ions, or molecules that have an odd number of electrons or where electron pairing is disrupted by specific circumstances.

How to Calculate Unpaired Electrons?

The following steps outline how to calculate the number of unpaired electrons (UE) using the formula UE = V – B – L.


  1. First, determine the number of valence electrons (V) in the atom.
  2. Next, determine the number of bonding electrons (B).
  3. Next, determine the number of lone pair electrons (L).
  4. Finally, calculate the number of unpaired electrons (UE) using the formula UE = V – B – L.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

number of valence electrons (V) = 8

number of bonding electrons (B) = 4

number of lone pair electrons (L) = 2