Word List Modern Physics

Alpha particle

The nucleus of a helium atom (two protons and two neutrons) emitted as radiation from a decaying heavy nucleus

Atomic number

The number of protons in the nucleus of an atom

Atomic line spectra

Spectral lines emitted or absorbed by low pressure gases when they are excited

Balmer series

Visible light produced by excited Hydrogen electrons

Binding energy per nucleon

Energy required to separate a nucleus into its nucleons, divided by the number of nucleons. This is a measure of the stability of a nucleus

Binding energy

The energy required to break a nucleus into its constituent protons and neutrons

Beta particle

High-energy electron emitted as ionizing radiation from a decaying nucleus

Bohr model

Model of the structure of the atom that attempted to correct the deficiencies of the Rutherford model for the atom

Continuous spectra

Separation of the electromagnetic spectrum into its discrete frequencies with no gaps (missing frequencies)

Electron volt

The energy gained by an electron moving across a potential difference of one volt; equivalent to 1.60 x 10^-19 J

Electron

Negatively charged subatomic particle which is usually found orbiting an atom, but gained/lost when atoms become ions

Electromagnetic spectrum

Family of waves that don't require a medium. Transverse, travel at 3.0x 10^8 m/s. e.g. light, x-ray

Energy absorption

The amount of energy taken in by an electron when excited

Energy level

Fixed quantities of energy which an electron can have in an atom

Ground state

Energy state of an atom with electrons at the lowest energy state possible for that atom

Gamma emission

Form of radioactive decay when an unstable nucleus emits extremely high-frequency electromagnetic radiation

Fusion

Nuclear reaction joining two low mass nuclei to make one more massive, more stable nucleus, releasing energy in the process

Fission

Nuclear reaction where one massive nucleus splits into two or more less massive nuclei, releasing energy in the process

Ionisation

The ability of nuclear radiation to take an electron off an atom, making it an ion