Question

The correct statements among the following is/are:

• A. Transition metals usually has very high melting point
• B. Second and third series metals have higher enthalpy of atomization than the corresponding elements in the first series
• C. Aqueous solutions of $L{a}^{3+}$ and $L{u}^{3+}$ are colourless
• D. All metals of actinoids can be attacked by $HCl$ but not be $HN{O}_3$

Answer 1

Answer: (A), (B), (C), (D)

All metals of actinoids can be attacked by $HCl$ but not be $HN{O}_3$

Transition metals usually has very high melting point due to the involvement of both $(n-1)d$ electrons and $ns$ electrons in metallic bonding.
Second and third series metals have higher enthalpy of atomization than the corresponding elements in the first series due to the greater extent of electrons involvement in metallic bonding.
The electronic configuration of $L{a}^{3+}=\left[Xe\right]$
The electronic configuration of $L{u}^{3+}=\left[Xe\right]4f^{14}$
So $L{a}^{3+}$ has zero $f$- electrons and $L{u}^{3+}$ has completely filled $4f$ subshell. Thus aqueous solutions of $L{a}^{3+}$ and $L{u}^{3+}$ are colourless.
All metals of actinoids can be attacked by $HCl$ but not be $HN{O}_3$ due to the formation of oxide layer