The chloride of which of the following elements will be coloured?

The "spin-only" magnetic moment [ in units of Bohr magneton,$(\mu_B)$ ] of $Ni^{2+}$ in aqueous solution would be (At. No. $Ni = 28$).

Given below are two statements:
Statement-$I$: The first ionization enthalpy of $Cr$ is lower than that of $Mn$.
Statement-$II$: The second and third ionization enthalpies of $Cr$ are higher than those of $Mn$.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following sets of ions contains colored ions?
$(1) \ Cu^{2+}$ $(2) \ Ti^{4+}$ $(3) \ Co^{2+}$ $(4) \ Fe^{3+}$

Which of the following statements is incorrect for the pair of elements $Zr$ and $Hf$?

Which of the following elements form interstitial compounds?