Question

which of these diagrams correctly shows the electron configuration for the atom with one more electron than the one shown above?

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals according to the Aufbau principle (low - energy orbitals first), Pauli exclusion principle (each orbital can hold a maximum of 2 electrons with opposite spins), and Hund's rule (electrons fill degenerate orbitals singly first with parallel spins). The given atom has 2 electrons in the 3s orbital and 2 unpaired electrons in the 3p orbitals.

Step2: Determine the next electron placement

The next electron will go into the 3p orbital. According to Hund's rule, when adding an electron to degenerate orbitals, it will pair up with an existing unpaired electron only after all degenerate orbitals have one electron each. So the new electron will pair up with one of the 3p electrons.

Answer:

The third option (where there are two electrons in 3s and three electrons in 3p with one pair and one unpaired electron) is correct.