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

Which of the following options represents the increasing order of the paramagnetic property of the ions?

Which of the $3d$ series of the transition metals exhibits the largest number of oxidation states and why?

How many unpaired electrons are there in $Ni^{2+}$?

The correct statement about iron includes:
$I$) The highest oxidation state of iron is $+ 6$ in $K_2FeO_4$.
$II$) The iron shows $+ 2$ oxidation state with six electrons in the $3d$ orbitals.
$III$) The common oxidation state of iron is $+ 3$ with five unpaired electrons in the $3d$ orbital.

Transition elements form complex compounds due to: