isotopes
an element with the same number of protons but a different number of neutrons
do isotopes have same or different atomic and mass numbers?
same atomic number, different mass number
what is relative atomic mass (Ar)?
an average mass taking into account the different masses and abundances of all the isotopes that make up the element
equation to calculate Ar
(mass isotope 1 x abundance) + (mass isotope 2 x abundance)/100