Chemistry

Question Analysis
This question involves subshell energy order for transition metals.
The main focus is on identifying the highest energy subshell that contains electrons in Fe, considering the Aufbau principle for elements beyond 18.

Key Concept Explanation
Subshell Energy for Transition Metals: For elements with atomic numbers 19–36, the 4s subshell fills before the 3d subshell (4s < 3d).
However, once electrons occupy the 3d subshell, the 3d subshell has higher energy than 4s.

Step-by-Step Solution
1. Neutral Fe has 26 electrons; full configuration: 1s²2s²2p⁶3s²3p⁶4s²3d⁶.
2. Identify the subshells with electr...