Question

Why are Cu, Ag and Ag included under transition elements even though they contain completely filled d−orbitals in their ground state?

Answer 1

Transition elements are elements with partly filled d orbitals (sometimes known as transition metals). Transition elements are defined by IUPAC as elements with a partly filled d subshell or elements that have the ability to produce stable cations with an incompletely filled d orbital.

Complete answer:
Any element that corresponds to the d-block of the current periodic table (which includes groups 3-12) is considered a transition element in general. Even the lanthanides and actinides, which make up the f-block, are considered transition metals. The f-block elements are commonly referred to as inner transition elements or inner transition metals because their f-orbitals are incompletely filled.
The d-orbitals of these metals are partially filled in their typical oxidation states. $C{{u}^{2+}}$ , for example, has a $3{{d}^{10}}$ configuration, while $A{{u}^{3+}}$ has a $5{{d}^{8}}$ configuration.
Cu may be found in two oxidation states (+1 and +2). An electron is removed from the S-orbital in the +1 oxidation state. However, when one electron is taken from the d-orbital in the +2 oxidation state, the orbital becomes incomplete ( $3{{d}^{9}}$ ). As a result, it's a transitional element. The d-orbitals of these metals are partially filled in their typical oxidation states. $C{{u}^{2+}}$ , for example, has a $3{{d}^{10}}$ configuration, while $A{{u}^{3+}}$ has a $5{{d}^{8}}$ configuration. Cu may be found in two oxidation states (+1 and +2). An electron is removed from the S-orbital in the +1 oxidation state.
However, when one electron is removed from the d-orbital in the +2 oxidation state, the d-orbital becomes incomplete ( $3{{d}^{9}}$ ). As a result, it's a transitional element.

Note:
When compared to other elements, transition metals are hard and have comparatively high densities.
Due to the presence of delocalized d electrons in metallic bonding, these elements have high boiling and melting temperatures.
The transition elements are also strong conductors of electricity due to the metallic bonding of the delocalized d electrons.