Answer:
Molybdenum (Mo) has an anomalous electron configuration due to the fact that it can have a half-filled or fully-filled d orbital which provides extra stability. The observed electron configuration of Mo is: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^1 4d^5. In this configuration, the electron configuration reaches the 5s orbital before filling the 4d orbital, resulting in the anomalous electron configuration for Mo.
