Chemistry

Question Analysis
This question evaluates the student's understanding of electron configuration and the Aufbau principle.

Key Concept Explanation
The Aufbau principle states that electrons fill the lowest-energy orbitals first. For potassium (atomic number 19), the correct order of filling is 1s, 2s, 2p, 3s, 3p, and 4s.

Step-by-step Solution
1. Identify the atomic number of potassium: 19.
2. Fill the orbitals in the order of increasing energy: 1s (2 electrons) → 2s (2 electrons) → 2p (6 electrons) → 3s (2 electrons) → 3p (6 electro...