An atom with 10 electrons must have how many electron shells?

• A. 1
• B. 4
• C. 3
• D. 2

Answer: (D)

Verified step by step guidance

1. Recall that electron shells correspond to principal energy levels, labeled as n = 1, 2, 3, etc., where each shell can hold a specific maximum number of electrons.
2. The first shell (n=1) can hold up to 2 electrons, and the second shell (n=2) can hold up to 8 electrons.
3. Add the maximum electrons in the first two shells: 2 (first shell) + 8 (second shell) = 10 electrons total.
4. Since the atom has 10 electrons, it fills the first shell completely and the second shell completely, meaning it uses 2 electron shells.
5. Therefore, an atom with 10 electrons must have 2 electron shells to accommodate all its electrons.