CHEM 121 MODULE 10: NUCLEAR
CHEMISTRY COMPREHENSIVE EXAM
QUESTIONS AND ANSWERS 2026/2027
UPDATE || 100% GUARANTEED PASS
1. Which type of radioactive decay results in the emission of a particle identical to a Helium-4
nucleus?
A. Beta decay
B. Alpha decay
C. Gamma radiation
D. Positron emission
Answer: B
Conceptual Explanation: Alpha decay involves the emission of an alpha particle, which
consists of two protons and two neutrons, identical to a Helium-4 nucleus.
2. In the process of beta decay, what change occurs to the atomic number of the parent
nuclide?
A. It decreases by 1
B. It increases by 1
C. It decreases by 2
,D. It remains unchanged
Answer: B
Conceptual Explanation: During beta decay, a neutron is converted into a proton and an
electron (beta particle). The addition of a proton increases the atomic number by 1.
3. Which of the following forms of electromagnetic radiation has the highest penetrating
power and no mass?
A. Gamma rays
B. Beta particles
C. Alpha particles
D. Positrons
Answer: A
Conceptual Explanation: Gamma rays are high-energy electromagnetic radiation with no
mass and high penetrating power, requiring lead or thick concrete to shield.
4. A sample of Iodine-131 has a half-life of 8 days. If the original sample is 100.0 g, how much
remains after 24 days?
A. 50.0 g
B. 12.5 g
C. 25.0 g
D. 6.25 g
, Answer: B
Conceptual Explanation: 24 days is exactly 3 half-lives (24/8 = 3). The amount remaining
is 100g * (1/2)^3 = 100/8 = 12.5 g.
5. Identify the missing product in the following nuclear equation: 238/92 U -> 234/90 Th + ?
A. 4/2 He
B. 0/-1 e
C. 0/+1 e
D. 1/0 n
Answer: A
Conceptual Explanation: The mass number decreases by 4 (238 to 234) and the atomic
number decreases by 2 (92 to 90), which corresponds to an alpha particle (4/2 He).
6. What is the primary factor that determines the stability of a nucleus?
A. The ratio of neutrons to protons
B. The total number of electrons
C. The temperature of the atom
D. The chemical bonds it forms
Answer: A
CHEMISTRY COMPREHENSIVE EXAM
QUESTIONS AND ANSWERS 2026/2027
UPDATE || 100% GUARANTEED PASS
1. Which type of radioactive decay results in the emission of a particle identical to a Helium-4
nucleus?
A. Beta decay
B. Alpha decay
C. Gamma radiation
D. Positron emission
Answer: B
Conceptual Explanation: Alpha decay involves the emission of an alpha particle, which
consists of two protons and two neutrons, identical to a Helium-4 nucleus.
2. In the process of beta decay, what change occurs to the atomic number of the parent
nuclide?
A. It decreases by 1
B. It increases by 1
C. It decreases by 2
,D. It remains unchanged
Answer: B
Conceptual Explanation: During beta decay, a neutron is converted into a proton and an
electron (beta particle). The addition of a proton increases the atomic number by 1.
3. Which of the following forms of electromagnetic radiation has the highest penetrating
power and no mass?
A. Gamma rays
B. Beta particles
C. Alpha particles
D. Positrons
Answer: A
Conceptual Explanation: Gamma rays are high-energy electromagnetic radiation with no
mass and high penetrating power, requiring lead or thick concrete to shield.
4. A sample of Iodine-131 has a half-life of 8 days. If the original sample is 100.0 g, how much
remains after 24 days?
A. 50.0 g
B. 12.5 g
C. 25.0 g
D. 6.25 g
, Answer: B
Conceptual Explanation: 24 days is exactly 3 half-lives (24/8 = 3). The amount remaining
is 100g * (1/2)^3 = 100/8 = 12.5 g.
5. Identify the missing product in the following nuclear equation: 238/92 U -> 234/90 Th + ?
A. 4/2 He
B. 0/-1 e
C. 0/+1 e
D. 1/0 n
Answer: A
Conceptual Explanation: The mass number decreases by 4 (238 to 234) and the atomic
number decreases by 2 (92 to 90), which corresponds to an alpha particle (4/2 He).
6. What is the primary factor that determines the stability of a nucleus?
A. The ratio of neutrons to protons
B. The total number of electrons
C. The temperature of the atom
D. The chemical bonds it forms
Answer: A
