Identify the complexes which are expected to be coloured. Give explanation.

Options

A. `[Ti (NO_(3))_(4)]`
B. `[Cu(NCCH_(3))]^(+) BF_(4)`
C. `[Cr (NH_(3))_(6)]^(3+) 3CI^(-)`
D. `K_(3)[VF_(6)]`

Explanation

`In [Ti(NO_(3))_(4)]`, O. N. of Ti is +4.
Hence, in Ti (IV) (1s_(2),2S^(2), 2p^(6),3S^(2), 3p^(6))` incomplete d-orbital is not present. So, itis colourlese.
(B) In [Cu(NCCH_(3))]^(+) BF_(4), O. N. of Cu is +1. Hence, in Cu(I)`[1s^(2), 2s^(2), 2p^(6) 3s^(2), 3p^(6), 3d^(10)]`incomplete d-orbital is not present. So it is also colourless
(C) In `Cr(NH_(3))_(6)]^(3+) 3CI^(-), O.N. of Cr is +3`. Hence, in Cr(III) `(1s^(2), 2s^(2), 2p^(6),3s^(2), 3p^(6) 3d^(3)` incomplete d-orbitals are present. So, it is coloured
(D) In `K_(3) [VF_(6)).O.N. of Vis +3. Hence, in V(III) `(1s^(2), 2s^(2) 2p^(6) 3s^(2), 3p^(6), 3d^(2))` incomplete d-orbital is present, so it is coloured
Hence, (C) and (D) are the correct answers.