Consider the following pairs of elements and identify the pairs of elements which have nearly same atomic radius.
$I$. $Y, La$
$II$. $Zr, Hf$
$III$. $Mo, W$
$IV$. $Cr, Mo$

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

Fill in the blanks:
$(a)$ The ground state electronic configurations of $Cr$ and $Cu$ are .......... and ..........,respectively.
$(b)$ Transition elements exhibit certain characteristic properties due to partially filled $d$-orbitals.
$(c)$ The general electronic configuration of transition elements is .......... .

The type of orbitals present in $Fe$ is

Why are the $E^{\circ}$ values for $Mn^{2+}$,$Ni^{2+}$,and $Zn^{2+}$ more negative than expected?

What is the observed electronic configuration of $Cu$?