The charge on $\alpha$-particle is ____ the charge on proton.
A.Twice
B.Thrice
C.Half
D.Same as

Hint: $\alpha$-particle is a charged helium particle. $\alpha$-particles are highly active and energetic rays.

Complete step by step answer:
$\alpha$-rays are emitted by radioactive elements because the unstable atom tries to gain stability. $\alpha$-particle is a positively charged particle. It is actually a helium nucleus which contains two protons and two neutrons. The charge on an $\alpha$-particle is +2, which is twice the charge on a proton and the mass of an $\alpha$-particle is four times the mass of a proton. It is represented by $He^{+2}$.
Hence, the charge on $\alpha$-particle is twice the charge on a proton.

Therefore, the correct answer is (A) twice.

Additional information: $\alpha$-particles have a low penetration power but a high ionization power. They can ionize a number of atoms at a short distance. They can produce burns on a human body. $\alpha$-rays can also produce artificial radioactivity in certain nuclei. The penetrating power of $\alpha$-rays is so low that a sheet of paper or a 3-cm layered air is enough to stop them. When an $\alpha$-particle is ejected towards a nucleus, its trajectory depends on the impact parameter of collision. The impact parameter (b) is the perpendicular distance of the initial velocity vector of the $\alpha$-particle from the centre of the nucleus.

Note: Don’t confuse between the charge of an $\alpha$-particle and a $\beta$-particle. $\alpha$-particles are +2 charged Helium nuclei while beta particles are -1 charged$\beta$- of electrons.