AP Chemistry / Unit 1: Atomic Structure and Properties
1.8 Valence Electrons and Ionic Compounds
Notes
Main-group elements form ions to reach noble-gas configurations.
- Group 1 → +1, group 2 → +2, group 16 → −2, group 17 → −1.
- Ionic formulas balance charges: $\mathrm{Mg^{2+}}$ and $\mathrm{Cl^-}$ give $\mathrm{MgCl_2}$.
Practice
The formula for aluminum oxide:
$2(+3)=3(2)$.
Calcium forms ions with charge:
Group 2.
Elements in the same group have similar chemistry because they have the same:
Same outer structure.
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