What digit (s) can be in the ones place of a number that has 5 as a facter

I'm not sure I understand what you're asking, but I will try my best-

a digit that can be in the ones place that has 5 as a factor would be a number ending in either 0 or 5, since we can only divide something by 5 if it ends in either of those numbers

for example: 55 divided by 5 is 11    130 divided by 5 is 26   10 divided by 5 is 2

The only digits that can be in the ones place is a 0 or a 5

... this is because

5 times 1 is 5 (ends in a 5)
5 times 2 is 10 (ends in a 0)
5 times 3 is 15 (ends in a 5)
5 times 4 is 20 (ends in a 0)

so on and so forth

hope this helped (:

Iwould think that the correct answer is 8.1

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table