5. An element whose highest occupied s sublevel and a nearby d sublevel

contain electrons

Transition Element

Explanation:

Transition elements are defined as those elements which can form at least one stable ion and has partially filled d-orbitals. They are also characterized by forming complex compounds and having different oxidation states for a single metal element.

Transition metals are present between the metals and the non metals in the periodic table occupying groups from 3 to 12. There general electronic configuration is as follow,

(n-1) d ¹⁻¹⁰ns ¹⁻²

The general configuration shows that for a given metal, the d sublevel will be in lower energy level as compared to corresponding s sublevel. For example,

Scandium is present in fourth period hence, its s sublevel is present in 4rth energy level so its d sublevel will be present in 3rd energy level respectively.

Hence, we can conclude that for transition metals the electron are present in highest occupied s sublevel and a nearby d sublevel.