CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which quantum-number set (n, l, m , mₛ) is allowed for an electron in a
ground-state arsenic atom?
A. 3, 3, –1, +½
B. 4, 2, –2, –½
C. 4, 1, +1, +½
D. 2, 2, 0, –½
Correct Answer: C
Explanation: l must be < n; m ranges from –l to +l. Only set C (4p electron) satisfies all
rules.
2. The first ionization energy of aluminum is lower than that of magnesium
because:
A. Al has a larger nuclear charge
B. Al’s outer electron occupies a higher-energy subshell
C. Mg has paired 3s electrons
D. Al contains more neutrons
Correct Answer: B
, Explanation: The 3p electron in Al is farther from the nucleus and less tightly held than
Mg’s 3s electron.
3. How many nodes (total) are present in a 4d orbital?
A. 3
B. 4
C. 5
D. 2
Correct Answer: A
Explanation: Total nodes = n – 1 = 3.
4. Arrange the following species in order of increasing atomic radius: P³⁻, S²⁻, Cl⁻,
Ar.
A. Ar < Cl⁻ < S²⁻ < P³⁻
B. P³⁻ < S²⁻ < Cl⁻ < Ar
C. Ar < P³⁻ < S²⁻ < Cl⁻
D. Cl⁻ < S²⁻ < P³⁻ < Ar
Correct Answer: A
Explanation: All are isoelectronic (18 e⁻); radius increases as nuclear charge decreases
(Ar has highest Z, P³⁻ lowest).
5. Which element has the electron configuration [Kr] 5s² 4d⁵?
A. Tc
2025/2026) — 30 High-Level Questions with
100% Correct Answers
1. Which quantum-number set (n, l, m , mₛ) is allowed for an electron in a
ground-state arsenic atom?
A. 3, 3, –1, +½
B. 4, 2, –2, –½
C. 4, 1, +1, +½
D. 2, 2, 0, –½
Correct Answer: C
Explanation: l must be < n; m ranges from –l to +l. Only set C (4p electron) satisfies all
rules.
2. The first ionization energy of aluminum is lower than that of magnesium
because:
A. Al has a larger nuclear charge
B. Al’s outer electron occupies a higher-energy subshell
C. Mg has paired 3s electrons
D. Al contains more neutrons
Correct Answer: B
, Explanation: The 3p electron in Al is farther from the nucleus and less tightly held than
Mg’s 3s electron.
3. How many nodes (total) are present in a 4d orbital?
A. 3
B. 4
C. 5
D. 2
Correct Answer: A
Explanation: Total nodes = n – 1 = 3.
4. Arrange the following species in order of increasing atomic radius: P³⁻, S²⁻, Cl⁻,
Ar.
A. Ar < Cl⁻ < S²⁻ < P³⁻
B. P³⁻ < S²⁻ < Cl⁻ < Ar
C. Ar < P³⁻ < S²⁻ < Cl⁻
D. Cl⁻ < S²⁻ < P³⁻ < Ar
Correct Answer: A
Explanation: All are isoelectronic (18 e⁻); radius increases as nuclear charge decreases
(Ar has highest Z, P³⁻ lowest).
5. Which element has the electron configuration [Kr] 5s² 4d⁵?
A. Tc
