Question

Why is `"Sn"^"2+"` diamagnetic?

Answer 1

If you look at the periodic table, you should see that the electron configuration for `"Sn"^0` is

`color(green)([Kr] 4d^10 5s^2 5p^2)`,

so its valence shell has ten `4d`, two `5s`, and two `5p` electrons.

Upon ionization, `"Sn"` will lose two of its highest-energy electrons to form `"Sn"^(2+)`.

The highest-energy electrons here are the `5p` electrons (by about `"8.55 eV"` above the energy of the `5s` electrons), so we now achieve an ionic electron configuration of

`color(blue)([Kr] 4d^10 5s^2)`.

Since the `4d` and `5s` subshells are entirely filled, there are no unpaired electrons and `"Sn"^(2+)` by definition is diamagnetic.