Mercurous ion is written as `Hg_(2)^(2+)` whereas cuprous ion is written as `Cu^(+)` . Explain.

Explanation

`""_(80)Hg:[Xe]4f^(14)5d^(10)6s^(2),Hg^(+)[Xe]4f^(14)5d^(10)6s^(1)`
In `Hg^(+)` ion, there is one unpaired electron and `Hg^(+)` (mercurous) salts are expected to be paramagnetic. But the magnetic moment of mercurous salts is zero which indicates that they are diamagnetic in nature. This is possible in case 6s electron has neenn used by two Hg atoms in bonding. Therefore, mercurous ion is `Hg^(2)^(2+)`.
`""_(29)Cu:[Ar]3d^(10)4s^(1),Cu^(+):[Ar]3d^(10)`.
In `Cu^(+)` ion, there is no unpaired electrons and `Cu^(+)` (cuprous) salts are expected to be diamagnetic. These are actually so. Therefore, cuprous ion is written as `Cu^(+)`.