1. Valence electrons are the outer-shell electrons that form bonds.
H has 1, C has 4, N has 5, O has 6, and F has 7 valence electrons.
2. Each atom bonds until its outer shell holds eight electrons.
Carbon has four valence electrons, so it forms four bonds and carries no lone pairs.
3. Nitrogen has five valence electrons, so it makes three bonds plus one lone pair.
Three bonds fill the shell to eight, and the two leftover electrons stay on nitrogen.
4. Oxygen has six valence electrons, so it makes two bonds plus two lone pairs.
Two bonds complete the octet, leaving four electrons as two lone pairs.
5. Fluorine has seven valence electrons, so it makes one bond plus three lone pairs.
A single bond finishes the octet, and the remaining six electrons form three lone pairs.
6. The pattern: for C–F, bonds = 8 − (valence electrons); H makes one.
This one rule predicts bond count and lone-pair count for every neutral first-row atom.
7. Summary
H = 1 bond · C = 4 bonds, 0 LP · N = 3 bonds, 1 LP · O = 2 bonds, 2 LP · F = 1 bond, 3 LP · bonds = 8 − valence electrons
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Six valence electrons, so it forms two bonds and keeps two lone pairs (as in water).
Three bonds plus one lone pair — 8 − 5 = 3 bonds, with the two leftover electrons as a lone pair.
It has four valence electrons; forming four bonds reaches an octet with nothing left over for lone pairs.
Three lone pairs — one bond completes the octet, leaving six electrons (three pairs) on fluorine.
Draw this on the whiteboard
Open the OChem Board whiteboard — benzene rings, wedge/dash bonds, and a clickable periodic table built in. No account needed.