Write an equation to represent `alpha` decay.

Explanation

To represent alpha decay, we start with a nucleus that has an atomic mass \( A \) and an atomic number \( Z \). The general equation for alpha decay can be written as:

\[ _{Z}^{A}X \rightarrow _{Z-2}^{A-4}Y + _{2}^{4}\text{He} \]

Where:
- \( _{Z}^{A}X \) is the parent nucleus (the original nucleus before decay).
...