The relative sizes of cations and anions depends on the
number of electron shells occupied
nuclear charge
nuclear charge
For ions in a given row in the periodic table,
the cations are smaller than the anions.
This is because the cations have one fewer electron shell occupied.
For ions in a given group in the periodic tableThis is because the cations have one fewer electron shell occupied.
Mg2+ and Na+ have two electron shells occupied (10 electrons for each).
S2– and Cl– have three electron shells occupied (18 electrons for each).
S2– and Cl– have three electron shells occupied (18 electrons for each).
the size of its monatomic ions increases going down the group because each successive member of the group has more electron shells occupied.
The relative sizes of ions from different rows of the periodic table may be able to be predicted on the basis of the number of electron shells occupied.
The monatomic cations in the diagram have one fewer electron shells occupied than the corresponding atom.
The monatomic anions in the diagram have the same number of electron shells occupied as the corresponding atom.
The monatomic anions in the diagram have the same number of electron shells occupied as the corresponding atom.