The $3d-$ elements show variable oxidation states. What is the maximum oxidation state shown by the element $Mn$?

The number of $4f$ electrons in the ground state electronic configuration of $Gd^{2+}$ is ........ .
[Atomic number of $Gd=64$]

The correct order of decreasing third ionisation enthalpy of $Ti$,$V$,$Cr$,and $Mn$ is:

Technetium,the element below manganese in the Periodic Table,would be expected to have high values for its:
$(I)$ melting point
$(II)$ boiling point
$(III)$ density

The set of elements which obey the general electronic configuration $(n-1)d^{1-10}ns^2$ is

Variable valency is shown by