Identify the complexes which are expected to be coloured.
a. `[Ti(NO_(3))_(4)]` , b. `[Cu(NC CH_(3))_(4)]^(o+) BF_(4)^(ɵ)`
c. `[Cr(NH_(3))_(6)]^(3+)3Cl^(ɵ)` , d. `K_(3)[VF_(6)]`

Explanation

`[Ti(NO_(3))_(4)]`
The oxidation state of `Ti` is `+4`
The atomic number of titanium is `22`
`Ti =[Ar] 3d^(2) 4s^(2)`
`Ti^(4+) =[Ar]`
No unpaired electrons So it is colourless
(ii) `[Cu(NCCH_(3))]^(4) BF_(4) Θ`
The oxidation state of `Cu` is `+1` The atomic number of copper is 28
`Cu =[Ar] 3d^(10) 4s^(1)`
`Cu = [Ar] 3d^(9)`
No unpaired electrons So it is colouless
(iii) `[Cr(NH_(3))_(6)]^(3+)3CI^(Θ)`
The oxidation sate of `Cr` is `+23`
The atomic number of chromium is 24
`Cr[Ar]3d^(10) 4s^(1)`
`Cr = [Ar] 3d^(8)`
It has 3 unpaired elctrons So it is coloured
(iv) `K_(3)[VE_(6)]`
The oxidation state of `V` is `+3`
The atomic number of vanadium is `+3`
The atomic number of vanatium is `+3`
`V =[Ar]3d^(3) 4s^(2)`
`V^(3+) = [Ar]3d`
It has 3 unpaired electrons So it coloured .