The element that usually does $NOT$ show variable oxidation states is

Which of the following elements has the maximum first ionization potential?

Addition of non-metals like $B$ and $C$ to the interstitial sites of a transition metal results in the metal becoming:

Determine whether the following statements are True $(T)$ or False $(F)$:
$(a)$ The atomic radii of the elements of the second transition series $(4d)$ are larger than those of the first transition series $(3d)$.
$(b)$ $Cr^{+}$,$Mn^{2+}$,and $Fe^{3+}$ have the same electronic configuration.
$(c)$ $Cr^{+}$,$Mn^{2+}$,and $Fe^{3+}$ have the same $d^5$ electronic configuration.

Although Zirconium $(Zr)$ belongs to the $4d$-transition series and Hafnium $(Hf)$ belongs to the $5d$-transition series, they show similar physical and chemical properties because . . . . . . .

The atomic radii of the elements are almost the same for which series?