CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Practice Questions with
100% Correct Answers
1. Which quantum-number set (n, l, m , mₛ) is permissible for an electron in a
ground-state potassium atom?
A. 4, 2, −1, +½
B. 3, 3, 0, −½
C. 4, 1, +2, +½
D. 3, 0, 0, +½
Correct Answer: D
Short Explanation: For potassium (Z = 19) the 3s subshell (n = 3, l = 0) is occupied; only
D satisfies l < n, |m | ≤ l, and mₛ = ±½.
2. The first ionization energy of sodium is 496 kJ mol⁻¹. What is the minimum
frequency of light that can ionize a single Na atom?
A. 1.24 × 10¹⁵ s⁻¹
B. 8.27 × 10¹⁴ s⁻¹
C. 1.24 × 10¹⁴ s⁻¹
D. 6.19 × 10¹³ s⁻¹
Correct Answer: C
Calculation: E = 4.96 × 10⁵ J / 6.022 × 10²³ = 8.24 × 10⁻¹⁹ J; ν = E/h = 8.24 × 10⁻¹⁹ J /
6.626 × 10⁻³⁴ J s ≈ 1.24 × 10¹⁵ s⁻¹ → choice A is per-atom value; the question asks
per-atom, so A is correct.
(Note: question phrasing corrected—answer is A.)
Correct Answer: A
, Rationale: Dividing the molar I.E. by Avogadro’s number gives the energy per atom; using
E = hν yields ν ≈ 1.24 × 10¹⁵ s⁻¹. Option B is half this value, C and D are orders of
magnitude too low.
3. Arrange the following ions in order of increasing ionic radius: Mg²⁺, Na⁺, O²⁻, F⁻.
A. Mg²⁺ < Na⁺ < F⁻ < O²⁻
B. O²⁻ < F⁻ < Na⁺ < Mg²⁺
C. Na⁺ < Mg²⁺ < F⁻ < O²⁻
D. F⁻ < O²⁻ < Na⁺ < Mg²⁺
Correct Answer: A
Explanation: Mg²⁺ and Na⁺ are smaller due to higher nuclear charge; isoelectronic with
Ne, radius decreases with Z. O²⁻ and F⁻ are larger; O²− has lower Z and largest radius.
4. How many nodes (total) does a 4d orbital possess?
A. 3
B. 4
C. 5
D. 2
Correct Answer: B
Explanation: Total nodes = n − 1 = 4 − 1 = 3; but the question asks for the d-orbital’s
radial + angular nodes: radial = n − l − 1 = 1, angular = l = 2 → total 3. (Correct total is 3;
choice A is correct.)
Correct Answer: A
Rationale: For any orbital, total nodes = n − 1 = 3. The 4d orbital has 1 radial and 2
angular nodes, summing to 3. Options B and C overcount; D is too low.
5. Which element has the largest third ionization energy?
A. Al
B. Si
2025/2026) — 30 High-Level Practice Questions with
100% Correct Answers
1. Which quantum-number set (n, l, m , mₛ) is permissible for an electron in a
ground-state potassium atom?
A. 4, 2, −1, +½
B. 3, 3, 0, −½
C. 4, 1, +2, +½
D. 3, 0, 0, +½
Correct Answer: D
Short Explanation: For potassium (Z = 19) the 3s subshell (n = 3, l = 0) is occupied; only
D satisfies l < n, |m | ≤ l, and mₛ = ±½.
2. The first ionization energy of sodium is 496 kJ mol⁻¹. What is the minimum
frequency of light that can ionize a single Na atom?
A. 1.24 × 10¹⁵ s⁻¹
B. 8.27 × 10¹⁴ s⁻¹
C. 1.24 × 10¹⁴ s⁻¹
D. 6.19 × 10¹³ s⁻¹
Correct Answer: C
Calculation: E = 4.96 × 10⁵ J / 6.022 × 10²³ = 8.24 × 10⁻¹⁹ J; ν = E/h = 8.24 × 10⁻¹⁹ J /
6.626 × 10⁻³⁴ J s ≈ 1.24 × 10¹⁵ s⁻¹ → choice A is per-atom value; the question asks
per-atom, so A is correct.
(Note: question phrasing corrected—answer is A.)
Correct Answer: A
, Rationale: Dividing the molar I.E. by Avogadro’s number gives the energy per atom; using
E = hν yields ν ≈ 1.24 × 10¹⁵ s⁻¹. Option B is half this value, C and D are orders of
magnitude too low.
3. Arrange the following ions in order of increasing ionic radius: Mg²⁺, Na⁺, O²⁻, F⁻.
A. Mg²⁺ < Na⁺ < F⁻ < O²⁻
B. O²⁻ < F⁻ < Na⁺ < Mg²⁺
C. Na⁺ < Mg²⁺ < F⁻ < O²⁻
D. F⁻ < O²⁻ < Na⁺ < Mg²⁺
Correct Answer: A
Explanation: Mg²⁺ and Na⁺ are smaller due to higher nuclear charge; isoelectronic with
Ne, radius decreases with Z. O²⁻ and F⁻ are larger; O²− has lower Z and largest radius.
4. How many nodes (total) does a 4d orbital possess?
A. 3
B. 4
C. 5
D. 2
Correct Answer: B
Explanation: Total nodes = n − 1 = 4 − 1 = 3; but the question asks for the d-orbital’s
radial + angular nodes: radial = n − l − 1 = 1, angular = l = 2 → total 3. (Correct total is 3;
choice A is correct.)
Correct Answer: A
Rationale: For any orbital, total nodes = n − 1 = 3. The 4d orbital has 1 radial and 2
angular nodes, summing to 3. Options B and C overcount; D is too low.
5. Which element has the largest third ionization energy?
A. Al
B. Si
