CHEM 210 Module 2 Exam (Portage Learning
2025/2026) — 30 High-Level Practice Questions with
100% Correct Answers
1. How many neutrons are present in the isotope ⁶⁴₃₀Zn?
A. 30
B. 34
C. 64
D. 94
Correct Answer: B
Explanation: Neutrons = mass number − atomic number = 64 − 30 = 34.
2. Which set of quantum numbers (n, l, m_l, m_s) describes the last electron filled in a
ground-state phosphorus atom?
A. 3, 1, 1, +½
B. 3, 2, 0, −½
C. 2, 1, −1, +½
,D. 3, 0, 0, −½
Correct Answer: A
Explanation: Phosphorus (Z = 15) ends with a 3p³ configuration; Hund’s rule places the third
electron in m_l = +1 with spin +½.
3. The first ionization energy of sodium is 496 kJ mol⁻¹. What is the maximum wavelength
of light that can photo-ionize a single Na atom?
A. 241 nm
B. 496 nm
C. 589 nm
D. 120 nm
Correct Answer: A
Explanation: E = hc/λ → λ = hc/E = (6.626×10⁻³⁴ J s)(2.998×10⁸ m s⁻¹)/(496×10³ J / 6.022×10²³)
≈ 2.41×10⁻⁷ m = 241 nm.
4. Which ion has the largest radius?
A. O²⁻
B. F⁻
, C. Na⁺
D. Mg²⁺
Correct Answer: A
Explanation: O²⁻ has the greatest negative charge and the smallest nuclear charge among the
choices, producing the largest electron-electron repulsion and largest radius.
5. Arrange the following species in order of increasing electronegativity: Si, P, S, Cl.
A. Si < P < S < Cl
B. Cl < S < P < Si
C. P < Si < S < Cl
D. Si < S < P < Cl
Correct Answer: A
Explanation: Electronegativity increases across a period; Cl is the most electronegative, Si the
least.
6. How many unpaired electrons are in a ground-state chromium atom?
A. 1
B. 4
2025/2026) — 30 High-Level Practice Questions with
100% Correct Answers
1. How many neutrons are present in the isotope ⁶⁴₃₀Zn?
A. 30
B. 34
C. 64
D. 94
Correct Answer: B
Explanation: Neutrons = mass number − atomic number = 64 − 30 = 34.
2. Which set of quantum numbers (n, l, m_l, m_s) describes the last electron filled in a
ground-state phosphorus atom?
A. 3, 1, 1, +½
B. 3, 2, 0, −½
C. 2, 1, −1, +½
,D. 3, 0, 0, −½
Correct Answer: A
Explanation: Phosphorus (Z = 15) ends with a 3p³ configuration; Hund’s rule places the third
electron in m_l = +1 with spin +½.
3. The first ionization energy of sodium is 496 kJ mol⁻¹. What is the maximum wavelength
of light that can photo-ionize a single Na atom?
A. 241 nm
B. 496 nm
C. 589 nm
D. 120 nm
Correct Answer: A
Explanation: E = hc/λ → λ = hc/E = (6.626×10⁻³⁴ J s)(2.998×10⁸ m s⁻¹)/(496×10³ J / 6.022×10²³)
≈ 2.41×10⁻⁷ m = 241 nm.
4. Which ion has the largest radius?
A. O²⁻
B. F⁻
, C. Na⁺
D. Mg²⁺
Correct Answer: A
Explanation: O²⁻ has the greatest negative charge and the smallest nuclear charge among the
choices, producing the largest electron-electron repulsion and largest radius.
5. Arrange the following species in order of increasing electronegativity: Si, P, S, Cl.
A. Si < P < S < Cl
B. Cl < S < P < Si
C. P < Si < S < Cl
D. Si < S < P < Cl
Correct Answer: A
Explanation: Electronegativity increases across a period; Cl is the most electronegative, Si the
least.
6. How many unpaired electrons are in a ground-state chromium atom?
A. 1
B. 4
