Which surface is larger – the neutral atom or the anion? Use the concept of effective nuclear charge to explain your observations.

Question

Which surface is larger – the neutral atom or the anion? Use the concept of effective nuclear charge to explain your observations.

I know anions are larger, but I can't exactly explain. Any help?

Answer 1

You're right. Anions ARE larger. Why?

1. Say we are looking at a F^-. It has 9 protons and 10 electrons. So those outside electrons are not held as strongly as in the neutral atom.
2. The outside electrons now have more negative charges squeezed into the space; negative charges repel so they move further apart and that makes the anion larger.