What is the electron configuration notation for the element with atomic number 26?

The correct notation for the electron configuration of the element with atomic number 26 is [Ar] 4s² 3d⁶. To understand why this is the right answer, it is essential to consider the arrangement of electrons as they fill atomic orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle.

Iron, which has an atomic number of 26, is located in period 4 of the periodic table and is a transition metal. The electron configuration begins with the noble gas core of argon ([Ar]), which accounts for the first 18 electrons. After argon, electrons fill the 4s orbital before filling the 3d orbitals. Following this order of filling, the next two electrons enter the 4s orbital, giving us 4s².

After the 4s orbital is filled, the remaining 6 electrons will occupy the 3d orbitals. According to Hund's rule, these electrons will distribute themselves among the available orbitals to minimize repulsion, resulting in a configuration of 3d⁶ for iron.

This electron configuration captures the correct distribution of electrons across the available energy levels and sub-levels for the given atomic number of 26