Calculate the `EAN` of the underlined atoms in the folloiwng complexes.
(a) ` [ul (Ca)(edta)]^(2-)`
(b) `[Ni (py) (en) (NH_(3))_(3)]^(2+)` .

Explanation

`[ul (Ca)(edta)]^(2-)`
`(Zo "of Ca" = 20)`
Let oxidation state of Ca be x
`:. + 1 xx (-4) = - 2`
`implies x = +2`
Coordination number of `("edta") =6`
`( :' "edta"^(4-)` is `"hexadentate ligand")`
:. EAN of `Ca = (20 -2)+2 xx 6 =30`
So EAN rule is not valide
`[Ni (py) (en) (NH_(3))_(3)]^(2+)`
`Ni (Z =28)`,
Let oxidation state of Ni be x
`:. x + 0 + 0+3 xx 0=2`
`implies x = +2`
[pyridine (py) and ammonia `(NH_(3))` are monoden tate ligand whereas ethy1enediamine (en) is bidentate ligand]
So, EAN of `Ni = (28 -2) + 2+2+2+xx 3 =38`
EAN rule is not valid .