Question

The nucleus ${}_{84}{}^{202}X$ emits an $\alpha$-particle and forms the nucleus Y . Represent this change in the form of an equation.

Answer 1

Given

Given nucleus is represented as${}_{84}{}^{202}X$.

Here the atomic number is 84 and the mass number is 202.

This nucleus emits an $\alpha$-particle by which the Y nucleus is formed.

$\alpha$-particle and emission of $\alpha$-particle

1. An alpha particle is identical to a helium nucleus$\left({}_2{}^{4}He\right)$. It contains 2 electrons, 2 protons and 2 neutrons.

2. When a nucleus emits an $\alpha$ particle, the mass number of the nucleus will be decreased by 4 and the atomic number of that nucleus will be decreased by 2.

3. Thus we can say that after the emission of an $\alpha$ particle ${}_{84}{}^{202}X$ nucleus will be converted into ${}_{84-2}{}^{202-4}X$that is${}_{82}{}^{198}Y$.

1. Representing the changes of the nucleus in the form of an equation we get:

${}_{84}{}^{202}X\to {}_{82}{}^{198}Y+{}_2{}^{4}He$.

Final answer

${}_{84}{}^{202}X\to {}_{82}{}^{198}Y+{}_2{}^{4}He$