ANSWER
Alpha particle...........> decreases the atomic number of an atom
Beta particles .............> increases the atomic number of the atom
Gamma particle ..........> does not change the atomic number of the atom
EXPLANATION
The three types of radioactive particles are;
1. Alpha particle
2. Beta particle
3. Gamma particle
Alpha particles has a positive charge with atomic number 2 and mass number 4
Any atom that gives off alpha particle, will have it atomic number drops by 2 and its mass number drops by 4
Hence, alpha particle decreases the atomic number of an atom
Beta particles; The atomic number of a beta particle changes, it can either be positive or negative
When an atom gives off a beta particle, the mass number number of the atom remains unchanged but the atomic number increases
Hence, beta particles increases the atomic number of the atom
Gamma particle is a neutral particle and it does not have any charge on it
When an atom gives off a gamma particle, the mass and atomic numbers of the atom remain unchanged
Hence, gamma particle does not change the atomic number of the atom