Rubidium has two naturally occurring isotopes: 85Rb, with mass 84.9118 amu and natural abundance 72.15%; and 87Rb, with mass 86.9092 amu and natural abundance 27.85%. Calculate the atomic mass of rubidium. View Available Hint(s) Rubidium has two naturally occurring isotopes: 85Rb, with mass 84.9118 amu and natural abundance 72.15%; and 87Rb, with mass 86.9092 amu and natural abundance 27.85%. Calculate the atomic mass of rubidium. 86.3529 amu 84.9118 amu 85.9105 amu 85.4681 amu