Diamond and Emerald are composed of which of the following respectively?

The melting point of $Zn$ is lower compared to those of the other elements of the $3d$ series because $-$

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 element from the following does $NOT$ exhibit a spin-only magnetic moment in the $+3$ oxidation state?

The calculated spin-only magnetic moment of $Cr^{2+}$ ion is: (in $text{ BM}$)

What is the atomic number of the first post-actinoid element?