Question

The highest oxidation state shown by transition element is:
A.+7by Mn
B.+8by Os
C.+8by Ru
D.+7by Fe

Answer 1

Basically, transition elements or transition metals are the elements that have partially filled d-orbitals. Moreover, the oxidation state of an atom provides insight into the number of electrons lost. Ideally, the oxidation state is either zero, positive or negative.

Complete step by step solution:
Transition elements are generally the elements that have partially filled d orbitals. Moreover, according to IUPAC, an element having a d subshell that is partially filled with electrons or an element that has the ability to form stable cations with an incompletely filled d orbital is known as transition element. Even the f-block elements comprising the lanthanides and the actinides can be considered as transition metals. However, since the f-block elements have incompletely filled f-orbitals so they are often referred to as inner transition elements or inner transition metals.
Now, some of the transition elements are Ni, Co, Fe, Ru, Ag, etc. The atomic and ionic radii of transition elements decrease from group 3 to group 6 due to the poor shielding offered by the small number of d-electrons. Moreover, the transition elements exhibit a wide variety of oxidation states in their compounds. For example, manganese shows all oxidation states from +2 to +7. However, some elements like Sc exhibit few oxidation states. The highest oxidation state i.e. +8 is shown by Os and Ru

Hence, option B and C both are correct.

Note:
These elements form colored compounds and ions. This color is further explained by the $d - d$ transition of electrons. Moreover, many paramagnetic compounds are formed by these elements because of unpaired electrons in the d-orbital.