In $\alpha$ -particles, the number of protons and electrons are                                   

He – atomic number = 2

Mass number = 4

No. of protons = 2.(Is equal to the atomic number)

 No. of electrons = 0.

Because it lose the $2\overline{e}$  and it gains the +2 ve charge.

Alpha particle is doubly ionised He atom or He Nucleus.