Which of the following represents the electron configuration of an atom with the atomic number 15?

The correct representation of the electron configuration for an atom with an atomic number of 15 is given in the choice that indicates 1s² 2s² 2p⁶ 3s² 3p³.

To understand why this is correct, we need to analyze the electron configuration step by step. Electrons are filled in atomic orbitals according to the Aufbau principle, which states that electrons occupy the lowest energy orbitals first.

1. The first energy level can hold a maximum of 2 electrons in the 1s orbital, so 1s² fills first.

2. The second energy level contains the 2s and 2p orbitals. The 2s can hold 2 electrons (2s²), and the 2p can hold a maximum of 6 electrons (2p⁶). Therefore, after filling these orbitals, we have 2 (from 1s) + 2 (from 2s) + 6 (from 2p) = 10 electrons.

3. For the third energy level, we start filling the 3s orbital, which holds 2 electrons (3s²). At this point, we have 12 electrons (