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An alpha particle is positively charged.
When a particle emits alpha decay...
2 protons and 2 neutrons are lost.
A beta particle is negatively charged.
When a particle emits beta decay...
e.g. When the thorium isotope 22890Th emits an alpha particle...
228 4 = 224 90 2 = 88
A neutron changes into a proton.
its proton number becomes 88 and its mass number becomes 224.
So it forms the radium isotope 22488Ra. e.g. When the potassium isotope 4019K emits a beta particle...
40 0 = 40 19 1 = 19 + 1 = 20
its proton number stays 40 and its mass number becomes 20.
So it forms the calcium isotope 4019Ca.
Gamma radiation is emitted as an electromagnetic wave.
Therefore, when a particle emits gamma decay...
No changes are made to the composition of the nucleus.
This is why gamma radiation is weakly ionising.