Question

Zinc and copper have similarity in their-
(A)- Group number
(B)- Electronic configuration
(C)- Number of electron present in d-subshell
(D)- Both are transition metals

Answer 1

. Please note that completely full or half-full orbitals are more stable than partially filled orbitals, and that not all d-block elements are transition elements.

Complete step by step answer:
-Group number of zinc is 12 whereas that of copper is 11 according to the periodic table.
-Electronic configuration:
Atomic number of zinc is 30. Therefore electronic configuration of zinc is-
$Z{{n}^{30}}=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{2}}$

Atomic number of copper is 29. Therefore its electronic configuration is -
$C{{u}^{29}}=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{1}}$

Electrons are filled in the atomic orbitals on the basis of the Aufbau principle which states that electrons are filled in the atomic orbitals in the increasing order of atomic energy level. The order therefore is : $1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 5d < 6p < 7s < 5f < 6d < 7p$ and so on. According to this the electronic configuration of copper should be $C{{u}^{29}}=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{9}}4{{s}^{2}}$ but it is not so. This is because of the exception that increased stability is provided by the completely filled and half-filled subshells as compared to partially filled subshells. Hence the correct electronic configuration of copper is $C{{u}^{29}}=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{1}}$ .

Looking at the electronic configurations of both zinc and copper, we find that both have different electronic configurations (hence option (B) is wrong), but the number of electrons present in d-subshell are same, that is, 10 electrons in d-subshell.
According to IUPAC (International Union of Pure and Applied Chemistry), transition metals are defined as “an element whose atom has a partially filled d-subshell or which can give rise to cations with an incomplete d-subshell.”
Hence zinc is not considered as a transition metal as it has completely filled the d-subshell. Zinc loses 2 electrons from its 4s subshell to form $Z{{n}^{2+}}$ cation. Although copper also has 10 electrons in its d-subshell but it can lose 2 electrons to form $C{{u}^{2+}}$ cation, 1 electron from 4s and 1 electron from 3d subshell leading to $3{{d}^{9}}$ configuration. Hence copper is a transition element, whereas zinc is not.
So, the correct answer is “Option C”.

Note: Exceptions should be kept in mind while solving electronic configuration related questions.
Similar exception can be seen in that of chromium$(C{{r}^{24}})$ . It has the electronic configuration as $C{{r}^{24}} = 1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{5}}4{{s}^{1}}$ instead of $C{{r}^{24}} = 1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{4}}4{{s}^{2}}$ due to the same reason as mentioned above.