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Solution


Q.

Which of the following statements are correct about Zn, Cd and Hg

A.  They exhibit high enthalpy of atomization as the d-subshell is full.

B.  Zn and Cd do not show variable oxidation state while Hg shows +I and +II.

C.  Compounds of Zn, Cd and Hg are paramagnetic in nature.

D.  Zn, Cd and Hg are called soft metals.

Choose the most appropriate from the options given below:                         [2024]
1 B, C only  
2 A, D only  
3 C, D only  
4 B, D only  

Ans.

(4)

      (A)(D) In transition series elements, melting point and enthalpy of atomization first increase, reaches a maxima and then decrease. This happens because unpaired d electrons have a strong tendency to participate in metallic bonding. Since Zn, Cd and Hg have comparatively low melting points in respective transition series, these are called soft metals.

(B) Mercury shows +1 and +2 oxidation states.

(C) Oxidation state of Zn and Cd is +2 in their compounds i.e. they have d10 configuration in their compounds, which makes them diamagnetic. Hg2+ is also d10 and diamagnetic. In +1 oxidation state, mercury exists as a dimer (Hg22+), hence in +1 oxidation state also mercury is diamagnetic.