Question

How will adding or taking away an electron affect atom size?

Answer 1

Removing an electron will make the atom larger, that is because of shielding effects are decreased.
Remember the core of the atom contains protons (positive charge) which is attracted to electrons (negative charge). So, they will attract, creating a smaller elctrons as you incease the size.
But, if you have less, it will make the atom larger cuz you have less electron from pulling the shell closer.