Understanding Radioactive Decay: Alpha, Beta, Gamma

1. In alpha decay, the nucleus emits:

An electron

A photon

A helium nucleus (2p + 2n)

A neutron only

Alpha particle identity. Alpha particle = helium-4 nucleus. It contains 2 protons and 2 neutrons, so it changes both z and a when emitted.

Explanation

Alpha particle identity. Alpha particle = helium-4 nucleus. It contains 2 protons and 2 neutrons, so it changes both z and a when emitted.

2. Alpha decay decreases mass number by 4.

True

False

Change in a for alpha decay. Loses 4 nucleons. Since an alpha particle contains 4 nucleons total, the mass number drops by 4.

Explanation

Change in a for alpha decay. Loses 4 nucleons. Since an alpha particle contains 4 nucleons total, the mass number drops by 4.

3. After alpha decay, atomic number z becomes:

Z+2

Z+1

Z-2

Unchanged

Change in z for alpha decay. Loses 2 protons. Because z counts protons, the atomic number decreases by 2.

Explanation

Change in z for alpha decay. Loses 2 protons. Because z counts protons, the atomic number decreases by 2.

4. In beta-minus (β-) decay, a neutron changes into a proton and an ______ is emitted.

β- transformation. β- emission is an electron. A neutron converts into a proton, so the nucleus gains one proton while emitting an electron.

Explanation

β- transformation. β- emission is an electron. A neutron converts into a proton, so the nucleus gains one proton while emitting an electron.

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5. In β- decay, the mass number usually:

Decreases by 1

Increases by 1

Stays the same

Decreases by 4

Nucleon count in β- decay. A neutron becomes a proton; total nucleons unchanged. Since one nucleon changes type but is not lost, a stays the same.

Explanation

Nucleon count in β- decay. A neutron becomes a proton; total nucleons unchanged. Since one nucleon changes type but is not lost, a stays the same.

6. In β- decay, atomic number z increases by 1.

True

False

Z change in β- decay. More protons after neutron → proton conversion. Because z counts protons, creating an extra proton increases z by 1.

Explanation

Z change in β- decay. More protons after neutron → proton conversion. Because z counts protons, creating an extra proton increases z by 1.

7. Gamma emission typically changes:

A only

Z only

Neither a nor z

Both a and z

Gamma as energy release. Gamma is energy release from an excited nucleus. It changes the nucleus’s energy state, not the number of protons or neutrons.

Explanation

Gamma as energy release. Gamma is energy release from an excited nucleus. It changes the nucleus’s energy state, not the number of protons or neutrons.

8. Which decay type often accompanies other decays to release extra energy?

Alpha only

Beta only

Gamma

Chemical decay

Gamma following other decays. Gamma often follows alpha or beta. After a decay, the daughter nucleus may be left excited and then emits gamma to drop to a lower energy state.

Explanation

Gamma following other decays. Gamma often follows alpha or beta. After a decay, the daughter nucleus may be left excited and then emits gamma to drop to a lower energy state.

9. Gamma rays are high-energy electromagnetic waves.

True

False

Gamma radiation type. They are photons. Gamma rays are part of the electromagnetic spectrum, but with very high frequency and energy.

Explanation

Gamma radiation type. They are photons. Gamma rays are part of the electromagnetic spectrum, but with very high frequency and energy.

10. Which radiation has a +2 charge?

Beta

Gamma

Alpha

Neutrino

Charge of radiation types. Alpha has 2 protons → +2 charge. Beta-minus has -1 charge, and gamma rays have no charge.

Explanation

Charge of radiation types. Alpha has 2 protons → +2 charge. Beta-minus has -1 charge, and gamma rays have no charge.

11. Beta-minus particles have charge ______.

Beta particle identity. They are electrons. Electrons carry a single negative charge, so β- has charge -1.

Explanation

Beta particle identity. They are electrons. Electrons carry a single negative charge, so β- has charge -1.

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12. A nucleus emits an alpha particle. Its mass number changes from 238 to:

240

237

234

232

Applying a-4 in alpha decay. 238-4=234. Alpha decay removes four nucleons, so you subtract 4 from the mass number.

Explanation

Applying a-4 in alpha decay. 238-4=234. Alpha decay removes four nucleons, so you subtract 4 from the mass number.

13. A nucleus has atomic number 92. After alpha decay its atomic number is:

94

93

90

88

Applying z-2 in alpha decay. 92-2=90. Losing two protons decreases atomic number by 2, changing the element.

Explanation

Applying z-2 in alpha decay. 92-2=90. Losing two protons decreases atomic number by 2, changing the element.

14. After β- decay, the element changes into a different element (because z changes).

True

False

Element identity depends on z. Z determines the element. Since β- decay increases z by 1, the nucleus becomes a different element.

Explanation

Element identity depends on z. Z determines the element. Since β- decay increases z by 1, the nucleus becomes a different element.

15. Which statements are correct? (Select multiple answers)

Alpha: a-4, z-2

Beta-minus: a same, z+1

Gamma: a-1, z-1

Gamma: a same, z same

Comparing decay rules. A, B, D are correct. Gamma changes energy only, alpha changes both a and z, and beta-minus changes z but not a.

Explanation

Comparing decay rules. A, B, D are correct. Gamma changes energy only, alpha changes both a and z, and beta-minus changes z but not a.

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16. Alpha particles are stopped easily because they interact strongly with matter.

True

False

Ionization and stopping power. They are heavy and charged, losing energy quickly. This strong interaction makes them highly ionizing but not very penetrating.

Explanation

Ionization and stopping power. They are heavy and charged, losing energy quickly. This strong interaction makes them highly ionizing but not very penetrating.

17. Beta particles are best described as:

Helium nuclei

Fast electrons (for β-)

Neutral photons

Sound waves

β- particle identity. β- is an electron. In nuclear decay it is often emitted at high speed, so it is described as a fast electron.

Explanation

β- particle identity. β- is an electron. In nuclear decay it is often emitted at high speed, so it is described as a fast electron.

18. Which is most penetrating?

Alpha

Beta

Gamma

None

Penetration ranking. Gamma penetrates most. It has no charge and interacts less often, so it can pass through thicker materials than alpha or beta.

Explanation

Penetration ranking. Gamma penetrates most. It has no charge and interacts less often, so it can pass through thicker materials than alpha or beta.

19. In beta-minus decay, the nucleus emits a beta particle to reduce its neutron-to-proton ratio.

True

False

Moving toward stability (n/z). Converting a neutron to a proton moves toward stability. β- decay helps neutron-rich nuclei adjust their neutron-to-proton ratio.

Explanation

Moving toward stability (n/z). Converting a neutron to a proton moves toward stability. β- decay helps neutron-rich nuclei adjust their neutron-to-proton ratio.