Which of the following species is paramagnetic? $Fe^{2+}, Zn^0, Hg^{2+}, Ti^{4+}$

The atomic radius of $Ag$ is closest to

Fill in the blanks:
$(a)$ The shielding effect of $d$-electrons is ......... effective than $p$-electrons.
$(b)$ $A$ decrease in exchange energy leads to a ......... in stability.
$(c)$ The maximum oxidation state of $Mn$ is ..........
$(d)$ The stability of $Mo(VI)$ and $W(VI)$ is found to be .......... than that of $Cr(VI)$.

The aqueous solution containing which one of the following ions will be colourless?

Which of the following transition elements have nearly the same atomic radii?

Identify the element for which the electronic configuration in the $+3$ oxidation state is $[Ar] 3d^5$: