Question

explain why transition metals show variable valencies or oxidation state

Answer 1

As transition metals have electrons in ns and (n-1)d orbitals

having almost comparable energy,thus easy to remove and hence show variable oxidation state such as when loose 1 or 2 electrons from ns subshell,valency becomes 1 or 2 respectively,when loose from ns as well as (n-1)d then depending on total no of electrons lost,variable valencies occurs.

Answer 2

Answer:

Because their valence electrons are in two separate sets of orbitals, (n-1)d and ns, transition elements have varying oxidation states. Because the energy difference between these orbitals is so small, both energy levels can be used to form bonds.

Explanation:

Why transition elements show variable oxidation states:

• The incomplete filling of d-orbitals in such a way that their oxidation states differ by unity, i.e. Fe²⁺ and Fe³⁺, causes the variability in oxidation states of transition metals.
• Furthermore, for heavier metals in a group, higher oxidation states are more stable, e.g. Mo⁺⁶ is more stable than Cr⁴⁺.

What are transition elements:

• Transition elements are elements with partially filled d orbitals (also known as transition metals).
• Transition elements are defined by IUPAC as elements with a partially filled d subshell or elements that have the ability to generate stable cations with an incompletely filled d orbital.
• The transition element's electrical configuration is (n-1)d⁵ ns¹ or (n-1)d¹⁰ ns¹.