Which element from the following exhibits the lowest number of different oxidation states?

The correct order of decreasing second ionisation enthalpy of $Ti(22), V(23), Cr(24)$ and $Mn(25)$ is

Which of the following does not contain silicon?

An ion with a definite magnetic moment (spin only) is:

Explain giving reasons:
$(i)$ Transition metals and many of their compounds show paramagnetic behaviour.
$(ii)$ The enthalpies of atomisation of the transition metals are high.
$(iii)$ The transition metals generally form coloured compounds.
$(iv)$ Transition metals and their many compounds act as good catalysts.

Which of the following substances will have the highest magnetic moment for its transition metal ion?