Which decay process releases an alpha particle, causing the atomic number to decrease by 2 and the mass number to decrease by 4?

Which decay process releases an alpha particle, causing the atomic number to decrease by 2 and the mass number to decrease by 4?

• A. Alpha Decay
• B. Beta Minus
• C. Beta Plus
• D. Gamma Decay

Answer: (A)

Alpha decay is when a nucleus ejects an alpha particle, which is a helium-4 nucleus made of two protons and two neutrons. Losing two protons lowers the atomic number by two, and removing four nucleons lowers the mass number by four. This exactly matches the described change, where the resulting nucleus has two fewer protons and four fewer nucleons, moving to a lighter element. Beta-minus decay would convert a neutron into a proton, increasing the atomic number by one while leaving the mass number unchanged. Beta-plus decay converts a proton into a neutron, decreasing the atomic number by one, again with the mass number unchanged. Gamma decay involves emitting energy as a photon without changing the number of protons or neutrons, so both Z and A stay the same. Thus, only alpha decay produces the specific decrease in both atomic number and mass number described.

Alpha decay is when a nucleus ejects an alpha particle, which is a helium-4 nucleus made of two protons and two neutrons. Losing two protons lowers the atomic number by two, and removing four nucleons lowers the mass number by four. This exactly matches the described change, where the resulting nucleus has two fewer protons and four fewer nucleons, moving to a lighter element.

Beta-minus decay would convert a neutron into a proton, increasing the atomic number by one while leaving the mass number unchanged. Beta-plus decay converts a proton into a neutron, decreasing the atomic number by one, again with the mass number unchanged. Gamma decay involves emitting energy as a photon without changing the number of protons or neutrons, so both Z and A stay the same. Thus, only alpha decay produces the specific decrease in both atomic number and mass number described.