What is an `alpha` particle?

What is an a (alpha) particle ?

An alpha particle is

An alpha particle is

Alpha particle is

What is the charge of an alpha particle?

What are the mass and charge of an alpha -particle?

A uranium 238 nucleus, originally at rest, emits and alpha particle. The alpha particle travels with a speed of v m/s. What is the recoil speed of the residual necleus?