α -particle consists of

Alpha particles are composite particles consisting of two protons and two neutrons tightly bound together. They are emitted from the nucleus of some radionuclides during radioactive decay, called alpha-decay.

$\alpha$ particle ${\to }_2{\mathrm{He}}^4$

No. of protons $\to 2$

No. of neutrons $\to 4-2=2$