The metal that shows the highest and maximum number of oxidation states is:

The $CORRECT$ ionisation energy order is

The element having general electronic configuration $3d^4 4s^1$ is

Compare the stability of the $+2$ oxidation state for the elements of the first transition series.

The spin-only magnetic moment value of $M^{3+}$ ion (in gaseous state) from the pairs $Cr^{3+}/Cr^{2+}$,$Mn^{3+}/Mn^{2+}$,$Fe^{3+}/Fe^{2+}$,and $Co^{3+}/Co^{2+}$ that has a negative standard electrode potential,is $B.M.$ (Nearest integer).

Which of the following pairs has similar ionic radii?