alleryStart learning →How many electrons does a nonmetal atom gain when it forms a monatomic anion?
AEnough to empty its valence shell
BExactly one, whatever the element
CEnough to fill its s and p orbitals
DEnough to match its period number
Answer & Solution
Correct answer: C. Enough to fill its s and p orbitals
1. A nonmetal forming an anion takes in electrons until its outer s and p orbitals are completely full.
2. Filling those orbitals gives it the electron arrangement of the next noble gas.
3. The charge on the anion is therefore just the number of electrons needed to complete that filling.
4. Oxygen needs two more electrons to reach the neon arrangement, so the oxide ion carries a two minus charge.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 7 "Chemical Bonding and Molecular Geometry", section Electronic Structures of Anions_
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