CART Nuclear Chemistry and Radioactivity 1 — Questions and Answers
Question 1: Which type of radiation has the greatest penetrating power?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutron particles
Correct answer: Gamma rays
Gamma rays are high-energy electromagnetic radiation with no mass or charge, allowing them to penetrate most materials except thick lead or concrete.
Question 2: What particles make up an alpha particle?
- 2 protons and 1 neutron
- 2 protons and 2 neutrons (Correct answer)
- 1 proton and 2 neutrons
- 2 electrons and 2 neutrons
Correct answer: 2 protons and 2 neutrons
An alpha particle is identical to a helium-4 nucleus, consisting of 2 protons and 2 neutrons, giving it a charge of +2.
Question 3: When an atom undergoes alpha decay, what happens to its atomic number?
- Increases by 2
- Decreases by 2 (Correct answer)
- Increases by 4
- Stays the same
Correct answer: Decreases by 2
In alpha decay, the nucleus loses 2 protons (and 2 neutrons), so the atomic number decreases by 2.
Question 4: Which statement best describes radioactive decay?
- A nucleus gains protons from its surroundings
- A nucleus spontaneously emits particles or energy to become more stable (Correct answer)
- A nucleus absorbs gamma rays to increase its energy
- A nucleus splits only when struck by an external neutron
Correct answer: A nucleus spontaneously emits particles or energy to become more stable
Radioactive decay is a spontaneous process in which an unstable nucleus releases energy or particles to reach a more stable configuration.
Question 5: What is the half-life of a radioactive isotope?
- The time for all atoms to decay completely
- The time for half of the radioactive atoms in a sample to decay (Correct answer)
- The energy released when half the sample decays
- The temperature at which decay rate doubles
Correct answer: The time for half of the radioactive atoms in a sample to decay
Half-life is the time required for exactly half of the radioactive nuclei in a sample to undergo decay.
Question 6: A beta particle emitted during beta-minus decay is identical to which particle?
- A proton
- A neutron
- An electron (Correct answer)
- A helium nucleus
Correct answer: An electron
A beta-minus particle is a high-energy electron emitted when a neutron in the nucleus converts to a proton.
Question 7: If a radioactive sample has a half-life of 5 years, what fraction of the original sample remains after 15 years?
- 1/2
- 1/4
- 1/8 (Correct answer)
- 1/16
Correct answer: 1/8
15 years = 3 half-lives; after each half-life the sample halves: (1/2)^3 = 1/8 of the original remains.
CART Nuclear Chemistry and Radioactivity 1
Which type of radiation has the greatest penetrating power?