Question

Which of the following electronic configuration of oxygen $\left(\text{O}\right)$ atom is correct?

• A. $$\begin{array}{c}\upharpoonleft \end{array}\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft \downharpoonright & \upharpoonleft \end{array}$$
• B. $$\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft & \upharpoonleft \end{array}$$
• C. $$\begin{array}{c}\upharpoonleft \end{array}\begin{array}{c}\upharpoonleft \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft \downharpoonright & \upharpoonleft \downharpoonright \end{array}$$
• D. $$\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{c}\upharpoonleft \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft \downharpoonright & \upharpoonleft \end{array}$$

Answer 1

The correct option is B $$\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft & \upharpoonleft \end{array}$$

According to Aufbau principle the electrons occupy the atomic orbitals with the lower energy before filling those with higher energy.

The maximum electrons that can be filled in subshells s, p, d are 2, 6, 10 respectively.

Oxygen has 8 electrons. So the electronic configuration of oxygen is $1s^2$ $2s^2$ $2p^4$.
According to Hund's rule, electron pairing in orbitals starts only when all available empty orbitals of the same energy are singly occupied.

So, the representation of electronic configuration would be-
$$\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{c}\upharpoonleft \downharpoonright \end{array}\begin{array}{ccc}\upharpoonleft \downharpoonright & \upharpoonleft & \upharpoonleft \end{array}$$