Chapter 10 · Chemical Bonding
10.2Representing Valence Electrons with Dots
9 min · two checks
Predict
How many dots belong on a Lewis symbol for nitrogen?
The idea
- Write Lewis symbols for main-group elements.
- Relate group number to valence-electron count.
A Lewis symbol places dots for valence electrons around the element symbol. For main groups, the count equals the group number using the older 1–8 labels, or the last digit of the modern group number: Group 1 has 1, Group 14 has 4, Group 17 has 7, Group 18 has 8. Pair dots only after four sides have one, so carbon is four single dots and oxygen is two pairs and two singles.
These dots are the electrons that bonding rearranges. Core electrons stay out of the drawing. Ions get brackets and a charge: Na⁺ has no dots and a 1+ charge, because it lost its one valence electron; Cl⁻ has eight dots and a 1− charge. The drawings are bookkeeping. They do not show distance from the nucleus.
Keep these
- Dots = valence electrons = main-group last digit.
- Spread dots before pairing.
- Ions are drawn in brackets with the charge.