Positive ions are smaller than the ions from which they are formed but negative ions are larger than the is from which they are formed explain why this is so

Positive ions are atoms that have lost an electron from its outtermost shell. It is positive because electrons are negative and the loss of something negative makes it a bit more positive.
A negative ion is larger than its original atom because it's gained an electron.

The more electrons an atomic has on its electron cloud, the bigger the atom.

Hopefully I didn't confuse you, good luck. ♡