Why is Potassium and Bromide KBr?

Why does Br not follow 2n2?

Br = 35 electrons, 2,8,18,7 why does the shell not fill to 32 and is happy with one of Potassium electrons.

Thank you kindly.

1 answer

a. Br does follow 2N^2

b. There aren't enough electrons to fill it with more than 7.
The first shell is full with 2, the second with 8 and the third with 18. That used up 28 and you have only 7 more electrons (35-28 = 7) so you place 7 electrons in the 4th shell. You don't have any more electrons to add to make it go to 32.