Element X has two stable isotopes, X-63 and X-65. X-63 has a molar mass of 62.93 g/mol and a relative abundance of 69.09 %. X-65 with an abundance of 30.91% has a molar mass of 64.93 g/mol.
What is the average atomic mass of X?
How many protons, electrons and neutrons are in Sr-87 (with a charge of +2)?