Question

A radio nucleus ${}_{Z}{{X}^{A}}$ emits an alpha particle and becomes $Y$. Mention the atomic number and the mass number o f$Y$. What do you call the conversion of one element into another element?

Answer 1

Hint: In a radioactive decay, the composition of the element changes according to the particles given out by it. Its composition changes because its mass number as well as the atomic number changes with every emission until it completely disappears. As the mass number is unique to every element, it gets converted to a new element altogether.

Complete solution:
A radioactive nucleus emits alpha, beta and gamma particles after a fixed interval of time. When an alpha particle is emitted, its atomic number increases by 2 and mass number decreases by 4. When a beta particle is emitted, its charge decreases by 1. There is no change in the mass or charge when gamma particles are emitted. Therefore, when ${}_{Z}{{X}^{A}}$ emits alpha particle, it changes to-
${}_{Z}{{X}^{A}}\to Y+\alpha $
$Y$ is such that,
$Y={}_{Z-4}{{X}^{A+2}}$
${}_{Z}{{X}^{A}}$ changes to a new element as its mass number has changed, the new element is $Y$.
When radioactivity occurs, due to the emission of different particles, the chemical composition of the atom changes, hence it converts into a new element. This process is known as transmutation.

Therefore, the new atomic number of $Y$ is $Z-4$ and its atomic number is $A+2$ and the process of conversion of one element into another is called transmutation.

Note:
The atomic number is the sum of the number of protons and neutrons in an atom. The atomic number is the total number of electrons revolving around an atom. Alpha particles are helium like particles, while beta particles are electrons or protons with very high energy. Gamma particles are electromagnetic radiation.