CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which quantum-numbers set (n, l, m_l, m_s) is the ONLY one that could represent
the highest-energy electron in a ground-state sulfur atom?
A. 3, 1, –1, +½
B. 3, 2, 0, –½
C. 3, 1, +1, –½
D. 2, 0, 0, +½
Correct Answer: A
Explanation: Sulfur (Z = 16) ends with the configuration [Ne] 3s² 3p⁴; the last electron is
added to the 3p subshell (l = 1). Option A is the only 3p choice; B is 3d (empty in
ground-state S).
2. Arrange the following species in order of INCREASING first-ionization energy:
Mg, Al, Si, P.
A. Mg < Al < Si < P
B. Al < Mg < Si < P
C. Mg < Si < Al < P
D. P < Si < Al < Mg
Correct Answer: A
, Explanation: Across Period 3, IE generally increases with Z_eff; the small drop between
Mg (3s²) and Al (3p¹) is overridden by the steady rise from Si to P. Thus Mg < Al < Si <
P.
3. Which orbital diagram violates the Pauli exclusion principle?
A. 2s: ↑↓
B. 2p: ↑ ↑ ↑
C. 2p: ↑↓ ↑
D. 1s: ↑↑
Correct Answer: D
Explanation: The 1s orbital (n = 1, l = 0, m_l = 0) can hold only two electrons with
opposite spins; two “up” arrows in one box violates Pauli.
4. The ⁴⁰Ar⁺ ion has how many neutrons?
A. 18
B. 20
C. 22
D. 40
Correct Answer: C
Explanation: Mass number 40 – atomic number 18 = 22 neutrons; ionization does not
change the nucleus.
5. Which pair of elements would form the MOST polar single bond?
A. C–H
B. N–O
C. H–F
D. S–Cl
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which quantum-numbers set (n, l, m_l, m_s) is the ONLY one that could represent
the highest-energy electron in a ground-state sulfur atom?
A. 3, 1, –1, +½
B. 3, 2, 0, –½
C. 3, 1, +1, –½
D. 2, 0, 0, +½
Correct Answer: A
Explanation: Sulfur (Z = 16) ends with the configuration [Ne] 3s² 3p⁴; the last electron is
added to the 3p subshell (l = 1). Option A is the only 3p choice; B is 3d (empty in
ground-state S).
2. Arrange the following species in order of INCREASING first-ionization energy:
Mg, Al, Si, P.
A. Mg < Al < Si < P
B. Al < Mg < Si < P
C. Mg < Si < Al < P
D. P < Si < Al < Mg
Correct Answer: A
, Explanation: Across Period 3, IE generally increases with Z_eff; the small drop between
Mg (3s²) and Al (3p¹) is overridden by the steady rise from Si to P. Thus Mg < Al < Si <
P.
3. Which orbital diagram violates the Pauli exclusion principle?
A. 2s: ↑↓
B. 2p: ↑ ↑ ↑
C. 2p: ↑↓ ↑
D. 1s: ↑↑
Correct Answer: D
Explanation: The 1s orbital (n = 1, l = 0, m_l = 0) can hold only two electrons with
opposite spins; two “up” arrows in one box violates Pauli.
4. The ⁴⁰Ar⁺ ion has how many neutrons?
A. 18
B. 20
C. 22
D. 40
Correct Answer: C
Explanation: Mass number 40 – atomic number 18 = 22 neutrons; ionization does not
change the nucleus.
5. Which pair of elements would form the MOST polar single bond?
A. C–H
B. N–O
C. H–F
D. S–Cl
