Determining the Count of Unshared Electrons

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<h3>Determining the Count of Unshared Electrons</h3>

Unshared electrons refer to outer (valence) electrons not part of a covalent bond. Shared electrons are those participating in a bond. Subtract the number of shared electrons (bonds x 2) from the number of valence electrons to discover number of unshared electrons.

Valence Electrons

Shared and unshared electrons are in the valence electron shell. Valence electrons form the “outside” of an atom and participate in bonding. It is important that shared and unshared electrons add up to the proper number of valence electrons.



Shared Electrons

Each bond represents two shared electrons. Salisbury University’s “Drawing Lewis Structures” illustrates this method. A molecule like NO2 is written as O=N-O and O-N=O. Each dash corresponds to a bond—a shared electron pair. O-N=O has a nitrogen (N) atom with six shared electrons, two from each bond.

Subtract Shared from Valence

For each atom, subtract shared electrons from number of valence electrons. Oxygen (O) has eight valence electrons. The left oxygen in O-N=O has 8 – 2 = 6 unshared electrons. The right oxygen has 8 – 2(2) = 8 – 4 = 4 unshared electrons. Nitrogen also has eight total valence electrons. In NO2 (O-N=O), the central nitrogen atom has 8 – 3(2) = 8 – 6 = 2 unshared electrons.

Dave Pennells

By Dave Pennells

Dave Pennells, MS, has contributed his expertise as a career consultant and training specialist across various fields for over 15 years. At City University of Seattle, he offers personal career counseling and conducts workshops focused on practical job search techniques, resume creation, and interview skills. With a Master of Science in Counseling, Pennells specializes in career consulting, conducting career assessments, guiding career transitions, and providing outplacement services. Her professional experience spans multiple sectors, including banking, retail, airlines, non-profit organizations, and the aerospace industry. Additionally, since 2001, he has been actively involved with the Career Development Association of Australia.