Word List Modern Physics
Alpha particle
Nucleus of a helium atom emitted as radiation from a decaying heavy nucleus.
Atomic number
Number of protons in the nucleus of an atom.
Atomic line spectra
Spectral lines emitted or absorbed by low-pressure gases when excited.
Balmer series
Visible light produced by excited Hydrogen electrons.
Binding energy per nucleon
Energy needed to separate a nucleus into its nucleons, indicating nucleus stability.
Binding energy
Energy required to break a nucleus into its constituent protons and neutrons.
Beta particle
High-energy electron emitted from a decaying nucleus.
Bohr model
Atom structure model correcting Rutherford model deficiencies.
Continuous spectra
Electromagnetic spectrum separated into discrete frequencies.
Electron volt
Energy gained by an electron moving across a potential difference of one volt.
Electron
Negatively charged subatomic particle orbiting an atom.
Electromagnetic spectrum
Family of waves not needing a medium, e.g., light, x-ray.
Energy absorption
Energy taken in by an electron when excited.
Energy level
Fixed energy quantities an electron can have in an atom.
Ground state
Atom's lowest energy state with electrons.
Gamma emission
Radioactive decay where unstable nucleus emits high-frequency radiation.
Fusion
Nuclear reaction combining low mass nuclei into a stable, more massive nucleus.
Fission
Nuclear reaction where a massive nucleus splits into smaller nuclei.
Ionisation
Ability of nuclear radiation to remove an electron from an atom.
Mass defect/deficit
Difference between the sum of nucleon masses and the actual nucleus mass.
Lyman series
Ultraviolet light spectrum produced by excited Hydrogen electrons.
Line spectrum
Narrow lines of color in a dark spectrum.
Isotope
Atoms of an element with the same protons but different neutrons.
Mass number
Sum of protons and neutrons in a nucleus.
Neutron
Uncharged particle in the atom nucleus.
Nuclear force
Attraction force between nucleons in the nucleus.
Orbital
Space around the nucleus where an electron is likely found.
Nucleus
Positively charged center of an atom with protons and neutrons.
Nucleons
Protons and neutrons in the atom nucleus.
Parent nuclide
Unstable nucleus decaying into lighter nuclei.
Paschen series
Infrared light spectrum produced by excited Hydrogen electrons.
Photoelectric effect
Metal surface releasing electrons when struck by photons.
Photon
Packet of light energy.
Quanta
Fixed amount of energy absorbed or emitted by matter.
Planck's constant
Number for calculating radiant energy based on radiation frequency.
Threshold frequency
Minimum frequency causing electron emission from a metal surface.
Work function
Minimum energy for electrons to escape a metal surface.
Rest mass
Particle mass when free.
Mass-energy conservation
Total mass-energy of reactants equals total mass-energy of products.
Ionisation energy
Energy to remove an electron from an atom.
Excitation energy
Energy to move an electron to
Alpha particle
Nucleus of a helium atom emitted as radiation from a decaying heavy nucleus.
Atomic number
Number of protons in the nucleus of an atom.
Atomic line spectra
Spectral lines emitted or absorbed by low-pressure gases when excited.
Balmer series
Visible light produced by excited Hydrogen electrons.
Binding energy per nucleon
Energy needed to separate a nucleus into its nucleons, indicating nucleus stability.
Binding energy
Energy required to break a nucleus into its constituent protons and neutrons.
Beta particle
High-energy electron emitted from a decaying nucleus.
Bohr model
Atom structure model correcting Rutherford model deficiencies.
Continuous spectra
Electromagnetic spectrum separated into discrete frequencies.
Electron volt
Energy gained by an electron moving across a potential difference of one volt.
Electron
Negatively charged subatomic particle orbiting an atom.
Electromagnetic spectrum
Family of waves not needing a medium, e.g., light, x-ray.
Energy absorption
Energy taken in by an electron when excited.
Energy level
Fixed energy quantities an electron can have in an atom.
Ground state
Atom's lowest energy state with electrons.
Gamma emission
Radioactive decay where unstable nucleus emits high-frequency radiation.
Fusion
Nuclear reaction combining low mass nuclei into a stable, more massive nucleus.
Fission
Nuclear reaction where a massive nucleus splits into smaller nuclei.
Ionisation
Ability of nuclear radiation to remove an electron from an atom.
Mass defect/deficit
Difference between the sum of nucleon masses and the actual nucleus mass.
Lyman series
Ultraviolet light spectrum produced by excited Hydrogen electrons.
Line spectrum
Narrow lines of color in a dark spectrum.
Isotope
Atoms of an element with the same protons but different neutrons.
Mass number
Sum of protons and neutrons in a nucleus.
Neutron
Uncharged particle in the atom nucleus.
Nuclear force
Attraction force between nucleons in the nucleus.
Orbital
Space around the nucleus where an electron is likely found.
Nucleus
Positively charged center of an atom with protons and neutrons.
Nucleons
Protons and neutrons in the atom nucleus.
Parent nuclide
Unstable nucleus decaying into lighter nuclei.
Paschen series
Infrared light spectrum produced by excited Hydrogen electrons.
Photoelectric effect
Metal surface releasing electrons when struck by photons.
Photon
Packet of light energy.
Quanta
Fixed amount of energy absorbed or emitted by matter.
Planck's constant
Number for calculating radiant energy based on radiation frequency.
Threshold frequency
Minimum frequency causing electron emission from a metal surface.
Work function
Minimum energy for electrons to escape a metal surface.
Rest mass
Particle mass when free.
Mass-energy conservation
Total mass-energy of reactants equals total mass-energy of products.
Ionisation energy
Energy to remove an electron from an atom.
Excitation energy
Energy to move an electron to
