AP Chemistry 2.5 Lewis Diagram Lesson

​AP Chemistry 2.5 Lewis Dots Diagram Discussion

By Lan Vu

Covalent Bonds

Share electrons to satisfy the octet rule. One covalent bond is 2 shared electrons

Steps

• Count and add up all valence electrons

• Pick the central atom (Least electronegative)

• Draw skeleton structure (bond = 2 electrons used)

• Add the remaining electrons in pairs until all the electrons have been used. Double or triple bonds might be used.

• Check that the octet rule is being satisfied for all elements (H & He are exceptions. They want 2 electrons only)

Multiple Choice

What is the correct Lewis Dot Structure for ammonia NH3

Multiple Choice

Which is the correct molecular structure for carbon dioxide?

​Violation of the Octet Rule

​Less than and Octet

• H & He only need 2 electrons (duet)

• B only need 6 electrons (hexet)

​More than an Octet

• Elements past Period 2 can have more than an octet because they can extend into the d orbital

​How to draw Lewis Structure for compounds that violate the octet rule?

• Same process for drawing Lewis Structure for a compound that follows the octet rule (even if they have more than 4 terminal atoms)

• Extra electrons after completing the octet

  • Place the extra electrons on the central atom

    • There can be up to two extra pairs on the central atom