Which type of radioactive decay involves the emission of a helium nucleus?
A
Beta decay
B
Gamma decay
C
Neutron emission
D
Alpha decay
Correct Answer: Option D — Alpha decay
Explanation:
Alpha decay occurs when an unstable atomic nucleus emits an alpha particle, consisting of two protons and two neutrons, equivalent to a helium nucleus. This process reduces the atomic number by two and mass number by four.