which transition element shows highest oxidation state

Answer:

Manganese is the 3d series transition element shows the highest oxidation state. The elctronic configuration of Manganese is

Mn(25) = [Ar} 3d⁵ 4s²

The reason why Manganese has the highest oxidation state is because the number of unpaired electrons in the outermost shell is more that is 3d⁵ 4s².

If we consider all the transition metals the highest oxidation state is eight and the element which shows +8 oxidation state are Ruthenium (Ru) and Os(Osmium).