Discrete energy
Emission spectrum representing different possible wavelengths of light emitted by an atom.
Emission spectrum
Series of bright lines representing the wavelengths that can be emitted by an atom.
Radioactivity
Spontaneous emission of particles and energy from an unstable nucleus.
Nuclear transmutation
Transformation of one element to another through nuclear reactions.
Nuclear fission
Splitting of a heavy nucleus into lighter nuclei, with the release of energy.
Critical mass
Minimum mass of fissile material needed to maintain a chain reaction.
Nuclear fusion
Joining of light nuclei to form a heavier nucleus, releasing energy.
Isotopes
Atoms with the same number of protons but different numbers of neutrons.
Radioactive decay
Unstable nuclei emit particles and energy spontaneously.
Half-life
The time required for half the quantity of a radioactive substance to undergo decay.
Unified atomic mass unit (u)
A standard unit of mass for atoms and molecules.
Mass defect
The difference between the mass of separated nucleons and the mass of the nucleus.
Binding energy
The energy required to disassemble a nucleus into its protons and neutrons.