Chemistry Definitions
define mass number
number of protons plus neutrons in a nucleus of an atom
define atomic number
number of protons in the nucleus of an atom
define relative atomic mass
average mass of an atom of an element / 1/12th mass of an atom of carbon-12
define relative molecular mass
average mass of a molecule / 1/12th mass of an atom of carbon-12
define isotope
atoms with the same numer of protons but different number of neutrons