8.28 Predict which of the following will be coloured in aqueous solution? Ti3+, V3+ , Cu+ , Sc 3+, Mn2+, Fe 3+ and Co 2+. Give reasons for each.

8.28 Metal ions which have valence electrons in d-orbital and in which d-d transition can take place will be coloured and the metal ions which have completely filled orbital or have d- orbital will be colourless as no d-d transition is possible in those configurations. Element Atomic Number Ionic State Electronic configuration in ionic state Ti 22 Ti3+ [Ar] 3d1 V 23 V3+ [Ar] 3d2 Cu 29 Cu+ [Ar] 3d10 Sc 21 Sc3+ [Ar] Mn 25 Mn2+ [Ar] 3d5 Fe 26 Fe3+ [Ar] 3d5 Co 27 Co2+ [Ar] 3d7 From the above table, it can be observed that only Sc3+ and Cu+ have either completely filled d- orbital or empty d-orbital. So, all other ions except Sc3+ and Cu+ will be coloured in aqueous solution because of absorption of radiations which fall in the visible region as on obtaining energy electrons jump from one d-orbital to another.

8.28 Predict which of the following will be coloured in aqueous solution? Ti³⁺, V³⁺ , Cu⁺ , Sc³⁺, Mn²⁺, Fe³⁺ and Co ²⁺. Give reasons for each.

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Payal Gupta | Contributor-Level 10

8 months ago

8.28 Metal ions which have valence electrons in d-orbital and in which d-d transition can take place will be coloured and the metal ions which have completely filled orbital or have d- orbital will be colourless as no d-d transition is possible in those configurations.

Element	Atomic Number	Ionic State	Electronic configuration in ionic state
Ti	22	Ti³⁺	[Ar] 3d¹
V	23	V³⁺	[Ar] 3d²
Cu	29	Cu⁺	[Ar] 3d¹⁰
Sc	21	Sc³⁺	[Ar]
Mn	25	Mn²⁺	[Ar] 3d⁵
Fe	26	Fe³⁺	[Ar] 3d⁵
Co	27	Co²⁺	[Ar] 3d⁷