Chapter 10 · Chemical Bonding
10.4Covalent Lewis Structures: Electrons Shared
10 min · two checks
Predict
How many shared pairs are in a triple bond?
The idea
- Draw single, double, and triple bonds as shared pairs.
- Count an octet when bonds and lone pairs are both present.
A covalent bond is a shared pair, drawn as two dots or as a line. Each atom in the pair counts both electrons toward its octet. Hydrogen is stable with two electrons, a duet, not an octet. A double bond is two shared pairs, as in O₂ when a full octet is required, and a triple bond is three, as in N₂. Lone pairs are valence electrons that are not shared; they still count toward the octet and they still affect shape.
Bonding pairs are the “glue.” Lone pairs are not idle: they repel other electron regions and they can be the site of a reaction. When you translate dots to lines, replace only the shared pairs. Leave lone pairs as dots. Forgetting them is the usual reason a later shape prediction comes out tetrahedral when it should be bent.
Keep these
- A line is one shared pair. Double and triple bonds are two and three pairs.
- Hydrogen stops at two electrons. Period-2 atoms usually stop at eight.
- Lone pairs count toward the octet and affect shape.