CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Real Questions with
100% Correct Answers
1. Which set of quantum numbers (n, l, mₗ, mₛ) is permissible for an electron in
a ground-state atom?
A. 3, 3, 0, +½
B. 2, 1, –2, –½
C. 4, 2, +2, +½
D. 1, 0, +1, –½
Correct Answer: C
Explanation: For n = 4, l can be 0–3; l = 2 (d) allows mₗ = –2…+2; mₛ = ±½ is
always allowed. A violates l ≤ n–1; B violates |mₗ| ≤ l; D violates |mₗ| ≤ l for l = 0.
2. The first ionization energy of aluminum is lower than that of magnesium
b ecause:
A. Al has a smaller atomic radius
B. Al’s outer electron occupies a higher-energy p orbital
C. Mg has more valence electrons
D. Al has a higher effective nuclear charge
Correct Answer: B
The 3p electron in Al is less tightly held than Mg’s 3s electron, despite the Zeff
increase, due to penetration/shielding differences.
, 3. How many nodes (total) are present in a 4s orbital?
. 2
A
B. 3
C. 4
D. 5
Correct Answer: B
Total nodes = n – 1 = 4 – 1 = 3 (one radial & two spherical).
4. Arrange the following species in order of increasing atomic radius: O²⁻, F⁻,
e, Na⁺
N
A. Na⁺ < Ne < F⁻ < O²⁻
B. O²⁻ < F⁻ < Ne < Na⁺
C. Ne < Na⁺ < F⁻ < O²⁻
D. Na⁺ < O²⁻ < F⁻ < Ne
Correct Answer: A
All are isoelectronic (10 e⁻); radius decreases with increasing Z: Na⁺ (11+) < Ne
(10+) < F⁻ (9+) < O²⁻ (8+).
5. What is the maximum number of electrons that can occupy the n = 3 shell?
. 8
A
B. 18
C. 32
D. 50
Correct Answer: B
2025/2026) — 30 High-Level Real Questions with
100% Correct Answers
1. Which set of quantum numbers (n, l, mₗ, mₛ) is permissible for an electron in
a ground-state atom?
A. 3, 3, 0, +½
B. 2, 1, –2, –½
C. 4, 2, +2, +½
D. 1, 0, +1, –½
Correct Answer: C
Explanation: For n = 4, l can be 0–3; l = 2 (d) allows mₗ = –2…+2; mₛ = ±½ is
always allowed. A violates l ≤ n–1; B violates |mₗ| ≤ l; D violates |mₗ| ≤ l for l = 0.
2. The first ionization energy of aluminum is lower than that of magnesium
b ecause:
A. Al has a smaller atomic radius
B. Al’s outer electron occupies a higher-energy p orbital
C. Mg has more valence electrons
D. Al has a higher effective nuclear charge
Correct Answer: B
The 3p electron in Al is less tightly held than Mg’s 3s electron, despite the Zeff
increase, due to penetration/shielding differences.
, 3. How many nodes (total) are present in a 4s orbital?
. 2
A
B. 3
C. 4
D. 5
Correct Answer: B
Total nodes = n – 1 = 4 – 1 = 3 (one radial & two spherical).
4. Arrange the following species in order of increasing atomic radius: O²⁻, F⁻,
e, Na⁺
N
A. Na⁺ < Ne < F⁻ < O²⁻
B. O²⁻ < F⁻ < Ne < Na⁺
C. Ne < Na⁺ < F⁻ < O²⁻
D. Na⁺ < O²⁻ < F⁻ < Ne
Correct Answer: A
All are isoelectronic (10 e⁻); radius decreases with increasing Z: Na⁺ (11+) < Ne
(10+) < F⁻ (9+) < O²⁻ (8+).
5. What is the maximum number of electrons that can occupy the n = 3 shell?
. 8
A
B. 18
C. 32
D. 50
Correct Answer: B
