Nuclear radiation and radioactive decay

Stable nuclei

Nuclei that contain a certain amount of neutrons compared to protons

Unstable nuclei

Nuclei with too few or too many neutrons

Radioactive decay

A random process in which an unstable nucleus will emit one or more types of nuclear radiation to become more stable

Nuclear radiation

Radiation emitted from an unstable nucleus during radioactive decay

Types of nuclear radiation

Alpha particle, beta particle, gamma ray, neutron

Alpha particle (α)

Consists of two neutrons and two protons and is identical to a helium nucleus

Beta particle (β)

A high speed electron ejected from the nucleus

Gamma ray (γ)

Electromagnetic radiation from the nucleus

Change to the nucleus due to alpha decay

The nucleus loses two protons and two neutrons

Effect of alpha decay on atomic and mass numbers

The mass number decreases by four and the atomic number decreases by two

Change to the nucleus due to beta decay

A neutron turns into a proton

Effect of beta decay on atomic and mass numbers

The atomic number increases by one and the mass number remains the same

Change to the nucleus due to gamma decay

There is no change to the particles in the nucleus

Effect of gamma decay on atomic and mass numbers

There is no change to the atomic or mass numbers

Geiger-Muller (GM) tube

A device that can detect ionising radiation and is used to measure the activity of a radioactive source

activity

the rate at which a source of unstable nuclei decays

becquerels (Bq)

the SI unit for activity

count-rate

the number of decays recorded each second by a detector