Exactly 200 of them
21 5s
None. It's written with only the digits '1' and '0'. If one were to divide 1,000 by 5, he would get a quotient of 200.
In the Rb atom, the electron configuration is [Kr]5s^1. This means there is 1 electron in the 5s sublevel of the Rb atom.
7
20
24
75
90
10
i think there are 18 digit 5s.
12