Question

How do alpha particles cause ionisation?

Answer 1

They rip electrons off of other molecules or atoms.

Explanation:

An `alpha`-particle is effectively a helium nucleus, that is 2 protons and two neutrons- without its two valence electrons.

As it is highly electron-deficient it will rip electrons from other molecules or atoms to become a stable helium atom, but in taking electrons from another molecule or atom, the `alpha`-particle turns that molecule or atom into a cation- a positively charged particle because it just lost its electrons.

The `alpha`-particle is considered as being strongly ionizing but has a very low penetration power, and can be stopped by a sheet of paper, or even by the air (As the particle will rip electrons from the oxygen and nitrogen in the air).