CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which set of quantum numbers (n, l, m<sub>, m<sub>) is valid for an electron in a
ground-state atom?
A. (3, 3, 0, +½)
B. (2, 1, −1, +½)
C. (4, 2, +3, −½)
D. (1, 0, +1, +½)
Correct Answer: B
Explanation: For n = 2, l can be 0 or 1; for l = 1, m<sub> ranges from −1 to +1. All
values are within limits and m<sub> is ±½, so the set is valid.
2. The first ionization energy of sodium is 496 kJ/mol. Which equation correctly
represents this process?
,A. Na(s) → Na⁺(g) + e⁻
B. Na(g) → Na⁺(g) + e⁻
C. Na⁺(g) → Na²⁺(g) + e⁻
D. Na(g) + e⁻ → Na⁻(g)
Correct Answer: B
Explanation: Ionization energy refers to the gaseous atom losing an electron: Na(g) →
Na⁺(g) + e⁻.
3. Arrange the following ions in order of increasing ionic radius: Mg²⁺, Na⁺, F⁻, O²⁻.
A. Mg²⁺ < Na⁺ < F⁻ < O²⁻
B. O²⁻ < F⁻ < Na⁺ < Mg²⁺
C. Na⁺ < Mg²⁺ < F⁻ < O²⁻
D. Mg²⁺ < O²⁻ < F⁻ < Na⁺
Correct Answer: A
, Explanation: All species are isoelectronic (10 electrons). Radius increases as nuclear
charge decreases: Mg²⁺ (12 p⁺) < Na⁺ (11 p⁺) < F⁻ (9 p⁺) < O²⁻ (8 p⁺).
4. How many unpaired electrons are in a ground-state sulfur atom (Z = 16)?
A. 0
B. 2
C. 4
D. 6
Correct Answer: B
Explanation: Sulfur’s electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁴. The 3p subshell
contains two orbitals with paired electrons and one orbital with two unpaired electrons
(Hund’s rule), giving 2 unpaired electrons.
5. Which element has the largest atomic radius?
A. Li
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which set of quantum numbers (n, l, m<sub>, m<sub>) is valid for an electron in a
ground-state atom?
A. (3, 3, 0, +½)
B. (2, 1, −1, +½)
C. (4, 2, +3, −½)
D. (1, 0, +1, +½)
Correct Answer: B
Explanation: For n = 2, l can be 0 or 1; for l = 1, m<sub> ranges from −1 to +1. All
values are within limits and m<sub> is ±½, so the set is valid.
2. The first ionization energy of sodium is 496 kJ/mol. Which equation correctly
represents this process?
,A. Na(s) → Na⁺(g) + e⁻
B. Na(g) → Na⁺(g) + e⁻
C. Na⁺(g) → Na²⁺(g) + e⁻
D. Na(g) + e⁻ → Na⁻(g)
Correct Answer: B
Explanation: Ionization energy refers to the gaseous atom losing an electron: Na(g) →
Na⁺(g) + e⁻.
3. Arrange the following ions in order of increasing ionic radius: Mg²⁺, Na⁺, F⁻, O²⁻.
A. Mg²⁺ < Na⁺ < F⁻ < O²⁻
B. O²⁻ < F⁻ < Na⁺ < Mg²⁺
C. Na⁺ < Mg²⁺ < F⁻ < O²⁻
D. Mg²⁺ < O²⁻ < F⁻ < Na⁺
Correct Answer: A
, Explanation: All species are isoelectronic (10 electrons). Radius increases as nuclear
charge decreases: Mg²⁺ (12 p⁺) < Na⁺ (11 p⁺) < F⁻ (9 p⁺) < O²⁻ (8 p⁺).
4. How many unpaired electrons are in a ground-state sulfur atom (Z = 16)?
A. 0
B. 2
C. 4
D. 6
Correct Answer: B
Explanation: Sulfur’s electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁴. The 3p subshell
contains two orbitals with paired electrons and one orbital with two unpaired electrons
(Hund’s rule), giving 2 unpaired electrons.
5. Which element has the largest atomic radius?
A. Li
