The least reactive metal is

An element is in $M^{3+}$ form. Its electronic configuration is $[Ar]3d^1$. The ion is:

The order of melting points of $Cr$,$Mo$,and $W$ is:

An element having the electronic configuration $[Ar]3d^24s^2$ belongs to

The transition element that has the lowest enthalpy of atomisation is

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 $Cr(VI)$.