In alpha decay, which statement is true?

• A. Occur s with light isotopes
• B. Atomic number increases by 2
• C. Emits gamma radiation only
• D. Alpha particle has charge +2 and mass 4 amu

Answer: (D)

In alpha decay, the nucleus ejects an alpha particle, which is essentially a helium nucleus made of two protons and two neutrons. That particle has a charge of +2 and a mass of about 4 atomic mass units. When this happens, the parent nucleus loses two protons and two neutrons, so its atomic number decreases by 2 and its mass number decreases by 4. Alpha decay mainly occurs in heavy nuclei, not light ones. Gamma radiation can accompany the process if the daughter nucleus is left in an excited state, but it’s not emitted instead of the alpha particle, so the statement that gamma radiation is emitted only is not correct.