Ionising radiation

What is it: 2 protons, 2 neutrons, helium nucleus

Relative mass: 4

Relative charge: +2

Ionisation: high

Stopped by: few cm of air or paper

What is it: an electron

Relative mass: 1/2000

Relative charge: -1

Ionisation: moderate

Stopped by: few cm of aluminium

What is it: electromagnetic wave

Relative mass: 0

Relative charge: 0

Ionisation: weak

Stopped by: lead or thick concrete