which orbital diagram represents oxygen (atomic number = 8)?

Explanation:

Step1: Determine the electron configuration of oxygen

Oxygen has an atomic number of 8. According to the Aufbau principle, electrons fill orbitals in the order of increasing energy: (1s<2s < 2p). The electron configuration of oxygen is (1s^{2}2s^{2}2p^{4}).

Step2: Apply Hund's rule for (2p) orbitals

Hund's rule states that electrons will occupy degenerate (equal - energy) orbitals singly as far as possible before pairing. For the (2p) sub - shell (which has 3 degenerate orbitals (p_x), (p_y), (p_z)), when filling 4 electrons:

• First, 3 electrons occupy each of the 3 (2p) orbitals singly (with parallel spins).
• The fourth electron pairs up with one of the already - occupied (2p) orbitals.

Answer:

The orbital diagram on the right (with (1s) as (\uparrow\downarrow), (2s) as (\uparrow\downarrow), and (2p) as (\uparrow\downarrow\uparrow\uparrow)) represents oxygen.