The general electronic configuration of the transition elements is
(n-1)d10, (n+1)s2
(n- 1)d1-10, (n + 1)s1-2
(n- 1)d1-10, np6,ns2
(n- 1)d1-10, ns1-2
Which of the following ions is colourless in solution?
V3+
Cr3+
Co2+
Sc3+
D.
Sc3+
(i) V (23) = [Ar]3d3, 4s2
V3+ = [Ar]3d2, 4s0 (two unpaired electrons)
(ii) Cr(24) = [Ar] 3d5, 4s1
Cr3+ = [Ar] 3d3, 4s0 (three unpaired electrons)
(iii) Co(27) = [Ar] 3d7, 4s2
Co2+ [Ar] 3d7, 4s0 (three unpaired electrons)
(iv) Sc(21) =[Ar] 3d7, 4s2
Sc3+ = [Ar]3d0, 4s0 (no unpaired electrons)
Thus, in Sc3+ no unpaired d-electron is present. Hence, no d-d transition is possible and it is colourless ion.
Select the coloured compound amongst the following .
(At. no. Ti= 22, Cr= 24, Cu= 29, Zn= 30)
TiCl4
CrCl3
ZnCl3
CuCl