IGCSE: Atomic Structure Simple

atom

atom

smallest particle of an element that retains its identity in a chemical reaction

Dalton's atomic theory

the first theory to relate chemical changes to events at the atomic level

electron

negatively charged subatomic particles

cathode ray

a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure

proton

a positively charged subatomic particle found in the nucleus of an atom

neutron

subatomic particles with no charge but with a mass nearly equal to that of a proton

nucleus

the tiny central core of an atom and is composed of protons and neutrons

atomic number

the number of protons in the nucleus of an atom of that element

mass number

the total number of protons and neutrons in an atom

isotope

an atom that has the same number of protons but different number of neutrons

atomic mass unit (amu)

one twelfth of the mass of a carbon-12 atom

atomic mass

a weighted average mass of the atoms in a naturally occuring sample of the element