Consider the following illustration of the periodic table. Identify which among the highlighted elements has an anomalous ground-state electron configuration. Justify your answer.

What is the electron configuration for a roentgenium atom?

Name the transition metal(s) in the second transition series that deviate(s) from the expected order of electron filling based on the Aufbau principle.

Looking at its position in the periodic table, determine the number of 5d electrons present in gold (Au).