How do you regroup on a subtraction ?

I hope this is what you're looking for. The concept of regrouping (borrowing) is so that students can see what actually happens in it. For example, to subtract 52 − 38, we write 52 as 50 + 2 (breaking it down into its tens and ones). Then, regrouping means that 50 + 2 becomes 40 + 12.

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