What is `alpha`-decay? What is the consequence of an `alpha`-decay on a radioactive element ?

Explanation

A radioactive transformation in which an `alpha`-particle is emitted is called `alpha`-decay. In an `alpha`-decay, the atomic number of the nucleus decreases by 2 and the mass number decreases by 4 .
Example : `""_(92)^(238)U to ""_(90)^(234)Th+""_(2)^(4)alpha`