Q. 233.7( 3 Votes )

Explain the follo

Answer :

The electronic configurations of the three are as follows - Sc3 + - [Ar]3d0 Co2 + - [Ar]3d7 and Cr3 + - [Ar]3d3

(a) Co2 + and Cr3 + have unpaired electrons. Thus, they are coloured in aqueous solution. Sc3 + has no unpaired electrons, and therefore they are colorless in aqueous solutions.

Reason: Unpaired electrons give colour to salts.

(b) Copper metal has a high enthalpy of atomization and ionization enthalpy. It requires much energy for it to turn into ions. Therefore the high energy required to convert Cu to Cu2 + is not compensated with the hydration enthalpy, and E is high and positive as compared to the others.

(c) Due to a phenomenon called lanthanoid contraction, the size of lanthanoids and its ions regularly decreases with an increase in atomic size. Thus covalent character between Lanthanide ion and OH - increases from La3 + to Lu3 + . Thus the basic character decreases.

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