Which of the following types of metals form the most efficient catalysts?

Predict which of the following will be coloured in aqueous solution: $Ti^{3+}, V^{3+}, Cu^{+}, Sc^{3+}, Mn^{2+}, Fe^{3+},$ and $Co^{2+}$. Give reasons for each.

Match the following:

List-$I$ (Element)	List-$II$ (Block)
$(A)$ $Ra$	$(I)$ $p$-block
$(B)$ $Uuq$	$(II)$ $s$-block
$(C)$ $Ds$	$(III)$ $f$-block
$(D)$ $Fm$	$(IV)$ $d$-block

The correct answer is

Mercury is a liquid metal because

What is the atomic number of an element having $ns^1$ electronic configuration and belonging to the $3d$ transition series?

Among the following transition elements,which one has the lowest first ionization energy?