On the basis of `EAN` rule predict the number of unpaired electrons and magnetic `(mu)` moment for the following compounds
(i) `[Cu (NH_(3))_(4)]^(2+)`
(ii) `[Cr(NH_(3))_(6)]Cl_(2)`

Explanation

Number of unpaired electrons present in the complex `=` Atomic number of next higher noble gas `-EAN` of central atom
Formula for magnetic moment `mu = sqrt(n(n+2)` B.M.
Where `n =` number of unpaired electrons.
(i) `EAN` of `Cu^(2+)` in `[Cu(NH_(3))_(4)]^(2+)` ion `=` Atomic number of `Cu -` Oxidation state of `Cu` in `[Cu(NH_(3))_(4)]^(2+)+ ` electrons gained by donation from ligands
`EAN=29 -2 + (2 xx 4)=35`
Number of unpaired electrons present in the complex `n = 36 -35 =1`
`mu = sqrt(n (n + 2))=sqrt(1(1 + 2))= sqrt3 = 1.73` B .M
(ii) `[Cr(NH_(3))_(6)]Cl_(2)`
`EAN` of `Cr^(2+)` in `[Cr(NH_(3))_(6)]Cl_(2)` complex `=` Atomic number of `Cr -` Oxidation state of `Cr` in `[Cr(NH_(3))_(5)]Cl_2+ ` electrons gained by donation from ligands
`EAN=24-2 + (2 xx 6)=34`
Number of unpaired electrons present in the complex `n = 36 - 34 =2`
`mu = sqrt(n (n + 2))= sqrt(2 (2 + 2)) = sqrt(8) = 2.83` B.M