Atoms of the same element that contains the same number of protons and electrons but different number of neutrons.
(% of isotope 1 x mass of isotope 1) + (% of isotope 2 x mass of isotope 2)
Ar = _______________________________________________________________
Use information from the table to calculate the relative atomic mass of this sample of Rubidium. Give your answer to one decimal place.
( 72 x 85 ) + ( 28 x 87 )
____________________________ = 85.6
Relative atomic mass = 85.6