1. The element rubidium (Rb) has two naturally occurring isotopes, ⁸⁵Rband ⁸⁷Rb.
   1. In your own words, explain how you could determine which isotope is the most abundant if you were not provided ANY other data than your periodic table. NO calculations required. (2 pts)

b. Provided with the information that Rubidium is 72.17% in ⁸⁵Rb and the atomic mass of ⁸⁵Rb is

84.911790 u, calculate the mass of ⁸⁷Rb.

Show all of your work for full marks, and watch sig figs and units.