Question

How many unpaired electrons are in a copper atom?

Answer 1

Hint: Copper is an element that has an atomic number ${\text{29}}$. One can write an electronic configuration that can give the idea about the number of electrons that are present in the orbitals of the copper element and decide the number of unpaired electrons.

Complete step by step answer:
1) First of all we will understand the concept of unpaired electrons. An unpaired electron is an electron that is present singly in an orbital of an atom and they don’t present in an electron pair form.
2) Now to know if the electrons present inside an orbital are paired or not, we need to find out the maximum electrons each subshell present in an atom can hold. If the electrons in the subshell are filled less than its full holding capacity then the electrons will remain unaired in that subshell.
3) There is only one orbital in an ‘s’ subshell that can hold a maximum of two electrons. The ‘p’ subshell in the orbital can hold six electrons maximum. The ‘d’ subshell in the orbital can hold a ten electrons maximum.
4) Now let us see the electronic configuration of the copper element as below,
${\text{Cu = 29 = 1}}{{\text{s}}^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^{10}}4{s^1}$
Now after observing the above electronic configuration we can say that there are fully filled ${\text{1s, 2s, 2p, 3s, 3p, 3d}}$ subshells where all the electrons are paired.
4) The last subshell which is ${\text{4s}}$ has only one electron which means there is one unpaired electron present in it.
Therefore, we can say that the Copper has only one unpaired electron.

Note:
The paired electrons in an orbital means the orbital is more stable than the unpaired electrons orbital. While writing the electronic configuration the filling of electrons should be done as per the Aufbau principle and Pauli’s exclusion principle.