Radioactive Decays

The nuclear phenomenon in which an unstable nucleus undergoes decay with the emission of some particles (α, β) and electromagnetic radiation (γ-rays) is called Radioactive Decay.

The rate of decay, i.e., the number of decays per unit time \[\left(-\frac{dN(t)}{dt}\right)\], is called Activity A(t).

The time in which half the substance (radioactive) is disintegrated is called the Half-Life Period of a radioactive substance.

The arithmetic average of the lives of all the nuclei present initially is called the Average Life of a radioactive element.

The phenomenon of emission of a nucleus of helium (₂He⁴) from a radioactive nucleus is called α-Decay.

The spontaneous emission of an electron (β⁻-decay) or a positron (β⁺-decay) from a radioactive nucleus is called β-Decay.

When a nucleus in an excited state spontaneously decays to its ground state and a photon is emitted with energy equal to the difference in the two energy levels of the nucleus, this is called γ-Decay.

The difference in the energy equivalent of the mass of the parent atom and that of the sum of masses of the products is called the Q-Value of the decay.

Q = [M_parent​ − M_products​]c²

Q = [m_X​ − m_Y​ − m_He​]c²

Q = [m_X ​− m_Y ​− m_e​]c²