Calculate the number of unpaired electrons in the following gaseous ions :
`Mn^(3+),Cr^(3+),V^(3+)`.

Explanation

`{:(Mn^(3+)(Z=26),:,[Ar]^(18)3d^(4),:,"Four unpaired electrons"),(Cr^(3+)(Z=23),:,[Ar]^(18)3d^(3),:,"Three unpaired electrons"),(V^(3+)(A=23),:,[Ar]^(18)3d^(2),:,"Two unpaired electrons"):}`