Question

which of the following orbital diagrams represent the ground state configuration for a neutral isolated oxygen atom? note that there may be more than one correct answer; select all that are correct.

Explanation:

Step1: Determine oxygen's electron - count

Oxygen has 8 electrons.

Step2: Recall electron - filling rules

Electrons fill orbitals according to the Aufbau principle (fill lower - energy orbitals first), Pauli exclusion principle (each orbital can hold at most 2 electrons with opposite spins), and Hund's rule (electrons in degenerate orbitals occupy them singly with parallel spins first).

Step3: Analyze the electron - filling for oxygen

The electron configuration of oxygen is $1s^{2}2s^{2}2p^{4}$. In the $1s$ orbital, there are 2 electrons with opposite spins, in the $2s$ orbital, there are 2 electrons with opposite spins, and in the $2p$ orbitals (3 degenerate $p$ orbitals), the first 3 electrons occupy the $2p$ orbitals singly with parallel spins and the 4th electron pairs up with one of them.

Answer:

The correct orbital diagram is the one where the $1s$ and $2s$ orbitals are filled with 2 electrons of opposite spins each, and the $2p$ orbitals have 4 electrons with the first 3 in separate orbitals with parallel spins and the 4th paired with one of them. So the correct option is the one that shows $\uparrow\downarrow$ in $1s$, $\uparrow\downarrow$ in $2s$, $\uparrow\downarrow\uparrow\uparrow$ in $2p$ (third option).