GC question about ion sizes

[onionlala]

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A question from destroyer, #256 says that strontium cation Sr2+ is smaller than sulfur anion S2- since Sr++ is a cation. So from my understanding, destroyer is trying to say that cations will always be smaller than anions. But are there exceptions? If you look at the electron configuration of Sr2+, it's [Kr] and the electron configuration of S2- is [Ar]. So Kr is obviously bigger than Ar since Kr has a higher level shell, then why would Sr2+ be larger than S2-? I'm really confused!

 

[jpark1800]

cations are smaller than anions...don't worry about the reason why

 

[Troyvdg]

bottom line, the more protons in the nucleus, the closer the valence electrons will pulled, thereby decreasing the ions size. You can only compare an isoelectronic series by using the standard trend of atomic radii, so when its not, the larger the positive charge, the smaller the ion