Question

The atomic number of Ni and Cu are 28 and 29 respectively. The electronic configuration $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}$represents:
(A) $C{{u}^{+}}$
(B) $C{{u}^{2+}}$
(C) $N{{i}^{2+}}$
(D) $Ni$

Answer 1

Hint: Electronic configuration of Cu is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{1}}$.When one electrons is lost from 4s orbital, then electronic configuration becomes \[1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}\]. When one electron is lost, a monovalent ion is formed.

Complete step by step solution:
Ni and Cu both are d block elements, the last electron enters in d orbitals, so they are known as d block elements. They belong to 3d series
3d series elements have general electronic configuration as \[[Ar]3{{d}^{1-10}}4{{s}^{1-2}}\].
Atomic number of Ni is 28 and it has electronic configuration as $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{8}}4{{s}^{2}}$.
When one electron is removed from 4s orbital, $N{{i}^{+}}$ is formed and leads electronic configuration as\[1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{8}}4{{s}^{1}}\].
When two electrons are removed from 4s orbital, $N{{i}^{2+}}$is formed and leads to electronic configuration as \[1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{8}}\].
Atomic number of Cu is 29, so expected electronic configuration according to Aufbau’s principle will be $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{9}}4{{s}^{2}}$.
As half and completely filled d orbitals are more stable, so to gain extra stability, one electron is transferred to 3d orbital as the energy difference between 3d and 4s is small, and it leads to completely filled d orbitals, so Observed electronic configuration is \[2{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{1}}\].
When one electron is removed from 4s orbital as 3d is completely filled, so electronic configuration becomes $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}$.

The electronic configuration $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}$represents (A) $C{{u}^{+}}$.

Note: Atomic number of Cu is 29, so expected electronic configuration according to Aufbau’s principle will be $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{9}}4{{s}^{2}}$. As half and completely filled d orbitals are more stable, so to gain extra stability, one electron is transferred to 3d orbital as energy difference between 3d and 4s is small, and it leads to completely filled d orbitals, so Observed electronic configuration is \[2{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}4{{s}^{1}}\]. In the same way, chromium has half -filled d orbitals.