Answer: I think 82.46
Explanation: The atomic number for strontium, or Sr on the periodic table, is 38. With knowing the atomic number, I multiplied that by the number of moles given.
38 × 2.17 = 82.46
I hope this helps!!
Simple conversion....
2.17 mol Sr x (6.022x10^23 atoms Sr / 1 mol Sr) = 1.31x10^24 atoms Sr
