Variable valency,in general,is exhibited by

Identify the element for which the electronic configuration in the $+3$ oxidation state is $[Ar] 3d^5$:

Which of the following series of transition elements has the general electronic configuration $[Kr] 4d^{1-10} 5s^{0-2}$?

Which one of the following is paramagnetic?

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 . . . . . . .

In the first transition series,the highest $B.P.$ and $M.P.$ is of