One of the elements shown on the following periodic table has an anomalous ground-state electron configuration. Which is it—red, blue, or green—and why?

Electron configuration describes the distribution of electrons in an atom's orbitals. It follows the Aufbau principle, which states that electrons fill orbitals starting from the lowest energy level to the highest. Understanding electron configuration is crucial for predicting an element's chemical properties and behavior, including its reactivity and bonding characteristics.

Anomalous electron configurations occur when an atom's electron arrangement deviates from the expected order based on the Aufbau principle. This typically happens in transition metals and some heavier elements, where stability is achieved by having half-filled or fully filled subshells. Recognizing these anomalies is essential for understanding the unique properties of certain elements.

The periodic table organizes elements based on their atomic number and electron configurations, revealing trends in properties such as electronegativity, ionization energy, and atomic radius. Elements in the same group often exhibit similar chemical behaviors due to their similar valence electron configurations. Analyzing these trends helps identify which element may have an anomalous configuration based on its position in the table.