atoms and molecules

atom

the basic unit of an element, an entity that is electrically neutral

Proton

sub-atomic particle that has a relative electric charge of +1 and its relative mass is 1

Neutron

sub-atomic particle that has a relative electric charge of 0 and its relative mass is 1

Electron

sub-atomic particle that has a relative electric charge of -1 and its relative mass is 1/1840

nucleus

contains protons and neutrons, make up most of the mass of an atom

proton number

number of protons in an atom, this number is unique to an element

nucleon number

number of protons and neutrons found in the nucleus of an atom

molecules

a group of two or more atoms that are chemically combined

chemical formula

number and types of atoms contained in a molecule

compound

a substance made of two different elements