AP Physics 2 Quiz: Types Of Radioactive Decay

What this quiz covers

This quiz focuses on Types Of Radioactive Decay, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Physics 2.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Gamma decay emitting a photon, with mass number decreasing by 4
2. Alpha decay emitting a $^{4}_{2}\text{He}$ nucleus (correct answer)
3. Beta-plus decay emitting a positron, with atomic number increasing by 2
4. Beta-minus decay emitting an electron, with mass number decreasing by 4

Explanation: This question tests understanding of types of radioactive decay. In alpha decay, a nucleus emits an alpha particle (helium-4 nucleus), which has 2 protons and 2 neutrons, causing the mass number to decrease by 4 and atomic number to decrease by 2. Here, Po-210 (Z=84, A=210) becomes Pb-206 (Z=82, A=206), showing exactly these changes: mass number drops by 4 (210→206) and atomic number drops by 2 (84→82). Beta decay would only change atomic number by 1, while gamma decay changes neither mass nor atomic number. Choice A incorrectly claims gamma decay changes mass number, revealing confusion about gamma rays being massless photons. When analyzing nuclear decay, always check both mass and atomic number changes to identify the decay type.

Question 2

1. $Z$ decreases by 1 because a proton becomes a neutron (correct answer)
2. $Z$ stays the same because only energy is emitted
3. $Z$ decreases by 2 because an alpha particle leaves
4. $Z$ increases by 1 because a neutron becomes a proton

Explanation: This question tests understanding of types of radioactive decay. A positron is the antiparticle of an electron with positive charge, emitted during beta-plus decay. In this process, a proton converts to a neutron plus a positron (and neutrino), decreasing the atomic number Z by 1. The mass number A remains constant since the total nucleon count doesn't change. Choice A describes beta-minus decay where Z increases, showing confusion between the two beta decay types. Choice C describes alpha decay, not positron emission. To distinguish beta decays, remember: positron emission means a proton becomes a neutron, so Z decreases.

Question 3

1. Alpha decay, emitting a helium nucleus
2. Beta-minus decay, emitting an electron
3. Beta-plus decay, emitting a positron (correct answer)
4. Gamma decay, changing the mass number

Explanation: This question tests understanding of types of radioactive decay. Sodium-22 changes to neon-22, where mass number remains 22 but atomic number decreases from 11 to 10. In beta-plus decay, a proton converts to a neutron plus a positron, decreasing Z by 1 while keeping A constant. The emitted positron (antimatter electron) carries away the positive charge. Beta-minus decay would increase Z, alpha decay would change both A and Z, and gamma decay changes neither. Choice B incorrectly suggests gamma decay changes mass number, showing confusion about photon emission effects. To distinguish beta decays, check whether atomic number increases (beta-minus) or decreases (beta-plus).

Question 4

1. A neutron, increasing the atomic number
2. A photon (gamma ray)
3. A helium nucleus (alpha particle)
4. An electron (beta-minus particle) (correct answer)

Explanation: This question tests understanding of types of radioactive decay. Carbon-14 transforms to nitrogen-14, where the mass number stays at 14 but the atomic number increases from 6 to 7. In beta-minus decay, a neutron converts to a proton plus an electron, increasing Z by 1 while keeping A constant. The emitted electron (beta-minus particle) carries away the negative charge. Alpha decay would decrease both A and Z, while gamma decay changes neither. Choice D incorrectly suggests neutron emission increases atomic number, showing confusion about how neutrons affect nuclear composition. When mass number stays constant but atomic number changes by 1, identify whether Z increases (beta-minus) or decreases (beta-plus).

Question 5

1. An alpha particle $^{4}_{2}\text{He}$
2. An electron (beta-minus particle) (correct answer)
3. A gamma photon that increases $A$ by 1
4. A positron (beta-plus particle)

Explanation: This question tests understanding of types of radioactive decay. The nucleus changes from K-40 (Z=19) to Ca-40 (Z=20), showing atomic number increases by 1 while mass number remains at 40. Beta-minus decay converts a neutron into a proton, emitting an electron and increasing Z by 1 without changing A since total nucleons are conserved. An alpha particle would decrease both Z and A, while a positron would decrease Z. Choice A incorrectly suggests gamma photons can increase mass number, reflecting the misconception that photons carry mass. When Z increases by 1 with constant A, the emitted particle must be an electron from beta-minus decay.

Question 6

1. Beta-plus decay, emitting a positron
2. Beta-minus decay, emitting an electron
3. Gamma decay, emitting a photon that lowers $A$ by 4
4. Alpha decay, emitting $^{4}_{2}\text{He}$ (correct answer)

Explanation: This question tests understanding of types of radioactive decay. The nucleus transforms from Po-210 (Z=84, A=210) to Pb-206 (Z=82, A=206), showing decreases of 2 in atomic number and 4 in mass number. Alpha decay emits a helium-4 nucleus containing 2 protons and 2 neutrons, producing exactly these changes: ΔZ = -2 and ΔA = -4. Beta decays would only change Z by 1 without affecting A, while gamma decay changes neither value. Choice B incorrectly suggests gamma decay can lower mass number, revealing the misconception that photons have mass. The simultaneous decrease of Z by 2 and A by 4 is the unique signature of alpha decay.

Question 7

1. Gamma decay, emitting a photon with no change in mass number or atomic number (correct answer)
2. Gamma decay, emitting a photon and increasing mass number by 1
3. Alpha decay, emitting a helium nucleus and decreasing mass number by 4
4. Beta-minus decay, emitting an electron and decreasing atomic number by 1

Explanation: This question tests understanding of types of radioactive decay. In gamma decay, an excited nucleus releases energy by emitting a gamma ray (high-energy photon) without changing its number of protons or neutrons, so both mass number and atomic number remain constant. The problem states the nucleus remains cobalt-60 after emitting radiation, meaning both the mass number (60) and atomic number (27) are unchanged, which is characteristic of gamma decay only. Choice D incorrectly claims gamma decay increases mass number, but photons have no mass and cannot add nucleons to the nucleus. When a nucleus emits radiation but remains the same isotope, it must be gamma decay releasing excess energy.

Question 8

1. $A$ stays the same and $Z$ decreases by 2
2. $A$ decreases by 2 and $Z$ decreases by 4
3. $A$ decreases by 4 and $Z$ decreases by 2 (correct answer)
4. $A$ decreases by 4 and $Z$ stays the same

Explanation: This question tests understanding of types of radioactive decay. An alpha particle consists of 2 protons and 2 neutrons (helium-4 nucleus), so when emitted, it removes exactly these nucleons from the parent nucleus. The mass number A decreases by 4 (total nucleons lost) and atomic number Z decreases by 2 (protons lost). This is the defining characteristic of alpha decay. Choice B reverses the changes, showing confusion about alpha particle composition. Choice C suggests only Z changes, which would be beta decay, not alpha. Remember that alpha particles are helium nuclei with specific composition: 2 protons and 2 neutrons.

Question 9

1. Beta-plus decay, emitting a positron
2. Beta-minus decay, emitting an electron
3. Gamma decay, emitting a photon
4. Alpha decay, emitting a helium nucleus (correct answer)

Explanation: This question tests understanding of types of radioactive decay. The uranium-238 nucleus changes to thorium-234, showing the mass number decreases from 238 to 234 (by 4) and the atomic number decreases from 92 to 90 (by 2). In alpha decay, a helium nucleus (2 protons and 2 neutrons) is emitted, which accounts for exactly these changes: A decreases by 4 and Z decreases by 2. Beta decay would change Z by 1 while keeping A constant, and gamma decay changes neither A nor Z. Choice B (gamma decay) represents a common misconception that any radioactive decay involves photon emission. To identify decay type, always check how both mass number and atomic number change.

Question 10

1. A beta-minus particle (electron), increasing atomic number by 1 (correct answer)
2. A gamma photon, increasing atomic number by 1
3. A beta-plus particle (positron), increasing mass number by 1
4. An alpha particle, increasing atomic number by 2

Explanation: This question tests understanding of types of radioactive decay. In beta-minus decay, a neutron converts to a proton by emitting an electron (beta particle), increasing the atomic number by 1 while mass number stays constant. Carbon-14 (Z=6, A=14) becomes nitrogen-14 (Z=7, A=14), showing atomic number increases by 1 (6→7) with unchanged mass number (14→14). Alpha decay would decrease both mass and atomic numbers, while gamma decay changes neither. Choice D incorrectly states beta-plus decay increases mass number, revealing the misconception that emitted particles add to nuclear mass rather than being created from existing nucleons. To identify decay type, compare initial and final atomic numbers and mass numbers systematically.

Question 11

1. Beta-plus decay emitting a positron, decreasing $Z$ by 1
2. Gamma decay emitting a photon, with no change in $A$ or $Z$ (correct answer)
3. Alpha decay emitting a $^{4}_{2}\text{He}$ nucleus, decreasing $A$ by 4
4. Beta-minus decay emitting an electron, increasing $Z$ by 1

Explanation: This question tests understanding of types of radioactive decay. In gamma decay, an excited nucleus (indicated by 'm' for metastable) releases excess energy as a photon without changing its nuclear composition, leaving both mass number (A) and atomic number (Z) unchanged. Technetium-99m (Z=43, A=99) emits a gamma ray to become ground-state technetium-99 (Z=43, A=99), with no change in either A or Z. Alpha decay would decrease both values, while beta decays would change Z. The other choices all incorrectly claim changes in A or Z, missing that gamma emission is purely an energy transition. When a metastable isotope loses its 'm' designation without changing element or mass, gamma decay has occurred.

Question 12

1. Beta-minus decay emitting an electron, decreasing atomic number by 1
2. Beta-plus decay emitting a positron, decreasing atomic number by 1 (correct answer)
3. Alpha decay emitting a $^{4}_{2}\text{He}$ nucleus, decreasing mass number by 4
4. Gamma decay emitting a photon, decreasing mass number by 4

Explanation: This question tests understanding of types of radioactive decay. In beta-plus decay (positron emission), a proton converts to a neutron by emitting a positron, decreasing the atomic number by 1 while mass number remains constant. Sodium-22 (Z=11, A=22) becomes neon-22 (Z=10, A=22), showing atomic number decreases by 1 (11→10) with unchanged mass number (22→22). Beta-minus decay would increase atomic number, while alpha decay would change both mass and atomic numbers. Choice B incorrectly claims beta-minus decay decreases atomic number, revealing confusion about the direction of charge change in beta decays. Remember that beta-plus decreases Z (proton lost) while beta-minus increases Z (proton gained).

Question 13

1. A positron (beta-plus particle)
2. A photon (gamma ray) that reduces mass number
3. A helium nucleus (alpha particle) (correct answer)
4. An electron (beta-minus particle)

Explanation: This question tests understanding of types of radioactive decay. Polonium-210 changes to lead-206, showing mass number decreases from 210 to 206 (by 4) and atomic number decreases from 84 to 82 (by 2). These changes match alpha decay perfectly, where a helium nucleus (2 protons, 2 neutrons) is emitted. Beta decays would only change Z by 1 while keeping A constant, and gamma decay changes neither value. Choice B incorrectly suggests gamma rays reduce mass number, confusing energy emission with particle emission. When both A and Z decrease by 4 and 2 respectively, alpha decay is the only possibility.

Question 14

1. Its mass number and atomic number stay the same (correct answer)
2. Its atomic number increases by 1
3. Its mass number decreases by 4
4. Its mass number increases because it gains energy

Explanation: This question tests understanding of types of radioactive decay. Gamma decay involves an excited nucleus releasing excess energy as a high-energy photon (gamma ray) without changing its nuclear composition. Since no nucleons are added or removed, both mass number A and atomic number Z remain unchanged. The nucleus simply transitions from a higher to lower energy state. Choice D incorrectly suggests mass increases with energy gain, confusing mass-energy equivalence with actual nucleon count. Choice B would indicate beta decay, not gamma. Remember that gamma rays are pure electromagnetic energy with no mass or charge, so they cannot change A or Z.

Question 15

1. Beta-minus decay, emitting an electron
2. Beta-plus decay, emitting a positron (correct answer)
3. Alpha decay, emitting $^{4}_{2}\text{He}$
4. Gamma decay, emitting a photon that decreases $Z$ by 1

Explanation: This question tests understanding of types of radioactive decay. The nucleus transforms from F-18 (Z=9) to O-18 (Z=8) with mass number constant at 18, indicating atomic number decreases by 1 while mass number is unchanged. Beta-plus decay converts a proton into a neutron plus a positron, decreasing Z by 1 without changing A since the total nucleon count remains constant. Beta-minus would increase Z, while alpha decay would change both values. Choice C incorrectly attributes Z decrease to gamma decay, revealing the misconception that photons can change nuclear composition. When atomic number decreases by 1 with unchanged mass number, beta-plus decay is the only possible process.

Question 16

1. An electron
2. A positron
3. A gamma photon
4. An alpha particle (correct answer)

Explanation: This question tests understanding of types of radioactive decay. The nucleus transforms from U-238 (Z=92, A=238) to Th-234 (Z=90, A=234), showing decreases of 2 in atomic number and 4 in mass number. An alpha particle is a helium-4 nucleus containing 2 protons and 2 neutrons, so its emission accounts for exactly these changes: ΔZ = -2 and ΔA = -4. Beta particles would only change Z by 1 with no A change, while gamma photons change neither value. The characteristic signature of alpha decay is always ΔZ = -2 and ΔA = -4, making particle identification straightforward. When both atomic and mass numbers decrease by these specific amounts, alpha decay is the only possible process.

Question 17

1. An alpha particle, decreasing atomic number by 1
2. A beta-minus particle (electron), decreasing atomic number by 1
3. A gamma photon, decreasing atomic number by 1
4. A beta-plus particle (positron), decreasing atomic number by 1 (correct answer)

Explanation: This question tests understanding of types of radioactive decay. In beta-plus decay (positron emission), a proton converts to a neutron by emitting a positron, decreasing atomic number by 1 while mass number stays constant. Fluorine-18 (Z=9, A=18) becomes oxygen-18 (Z=8, A=18), showing atomic number decreases by 1 (9→8) with unchanged mass number (18→18). Beta-minus would increase Z, while alpha decay would change both A and Z. Choice B incorrectly claims beta-minus decreases atomic number, confusing the effects of electron emission (Z increases) with positron emission (Z decreases). To distinguish beta decays: beta-minus adds positive charge (Z+1), beta-plus removes positive charge (Z-1).

Question 18

1. Alpha decay, decreasing mass number by 4
2. Gamma decay, emitting a photon (correct answer)
3. Beta-plus decay, increasing atomic number by 1
4. Beta-minus decay, increasing mass number by 1

Explanation: This question tests understanding of types of radioactive decay. The excited cobalt-60 nucleus (marked with *) becomes ground-state cobalt-60 with no change in mass number (60) or atomic number (27). Gamma decay occurs when an excited nucleus releases energy as a photon without changing its composition. Alpha decay would decrease A by 4 and Z by 2, while beta decays would change Z by 1. Choice C incorrectly claims beta-minus decay increases mass number, revealing a misconception that particle emission always changes A. When a nucleus transitions from excited to ground state with unchanged A and Z, gamma decay is occurring.

Question 19

1. Beta-minus decay, emitting an electron
2. Alpha decay, emitting $^{4}_{2}\text{He}$
3. Beta-plus decay, emitting a positron (correct answer)
4. Gamma decay, emitting a photon that increases $Z$ by 1

Explanation: This question tests understanding of types of radioactive decay. The nucleus changes from Na-22 (Z=11) to Ne-22 (Z=10) with mass number constant at 22, showing atomic number decreases by 1 while mass number remains unchanged. Beta-plus decay converts a proton into a neutron plus a positron, decreasing Z by 1 without changing A since total nucleon count stays constant. Beta-minus decay would increase Z by 1, while alpha decay would change both Z and A. Choice B incorrectly suggests gamma decay can increase Z, reflecting the misconception that photons can change nuclear composition. To identify beta decay type, check the direction of Z change: increasing Z means beta-minus, decreasing Z means beta-plus.

Question 20

1. Alpha decay emitting a $^{4}_{2}\text{He}$ nucleus, decreasing atomic number by 2
2. Gamma decay emitting a photon, with no change in $A$ or $Z$ (correct answer)
3. Beta-minus decay emitting an electron, increasing mass number by 1
4. Beta-plus decay emitting a positron, increasing atomic number by 1

Explanation: This question tests understanding of types of radioactive decay. In gamma decay, an excited nucleus releases energy as a photon without changing its composition, so both mass number (A) and atomic number (Z) remain unchanged. The excited Co-60 nucleus (denoted by the asterisk in some notations) emits a gamma ray and becomes ground-state Co-60, maintaining Z=27 and A=60. Alpha decay would decrease both A and Z, while beta decays would change Z. Choice D incorrectly states beta-plus decay increases atomic number, showing confusion about positron emission decreasing proton count. When a nucleus remains the same element with the same mass number after decay, only gamma emission is possible.