Units

Radioactivity Units

• Becquerel (Bq): This is the standard unit for measuring radioactivity. One Becquerel equals one disintegration, or transformation, per second.

• Gray (Gy): Gray is the standard unit of absorbed radiation dose. It represents the absorption of one joule of radiation energy by one kilogram of matter.

• Sievert (Sv): This unit measures the biological effect of absorbed radiation, considering the varying harmful effects of different forms of ionising radiation. Like the Gray, it is joules per kilogram, but also factors in the type of radiation and the sensitivity of the tissues targeted.

Particle Units

• Atoms: Atoms are the fundamental units of matter, consisting of a nucleus containing protons and neutrons, surrounded by electrons.

• Moles: A mole is a method of expressing the amount of a substance. It is the number of atoms in exactly 12g of carbon-12. This number is known as Avogadro’s number, and is approximately 6.02 x 10^23.

• Unified atomic mass units (u): One unified atomic mass unit is approximately the mass of one nucleon (either a proton or a neutron) and is roughly 1.66 x 10^-27 kg.

• Electronvolts (eV): An electronvolt is a unit of energy. It’s the amount of kinetic energy gained or lost by a single electron moving across an electric potential difference of one volt.

Additional Terms

• Half-life: The time it takes for half of the atoms in a radioactive sample to decay. This is a probabilistic measure; half-life is the time at which there is a 50% chance an atom will have decayed.

• Isotopes: Isotopes are variations of a particular chemical element, having the same number of protons, but a different number of neutrons. This means they have the same atomic number, but different atomic weights.

• Fission and Fusion: Fission is the process of one atom splitting into two smaller ones, often releasing a large amount of energy. Fusion is the process of two small atoms joining to form a larger one, also often releasing a large amount of energy.