electronic configuration of Iron. include details about subshells.

Iron is a chemical element with the symbol Fe and atomic number 26. The electronic configuration of an atom tells us how the electrons are distributed in the atom's energy levels.

Here is the step-by-step electronic configuration of Iron:

1. The first energy level (n=1) has one subshell, the 1s subshell. This can hold up to 2 electrons. So, we start by filling up this subshell. Now we have 2 out of 26 electrons of Iron placed. The configuration is now 1s².

2. The second energy level (n=2) has two subshells, the 2s and 2p. The 2s subshell can hold up to 2 electrons and the 2p subshell can hold up to 6 electrons. We fill up the 2s subshell first, then the 2p subshell. Now we have 10 out of 26 electrons placed. The configuration is now 1s² 2s² 2p⁶.

3. The third energy level (n=3) has three subshells, the 3s, 3p, and 3d. The 3s and 3p subshells can hold up to 2 and 6 electrons respectively, and the 3d subshell can hold up to 10 electrons. We fill up the 3s and 3p subshells first, then we start filling up the 3d subshell. However, we can only place 6 electrons in the 3d subshell at this point because we only have 6 electrons left. Now we have all 26 electrons placed. The configuration is now 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶.

4. The fourth energy level (n=4) has the 4s subshell, which we fill with the remaining 2 electrons. The final electronic configuration of Iron is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶.

Note: The 4s subshell is filled before the 3d subshell because it has a lower energy level. This is an exception to the Aufbau principle, which states that electrons fill up the lowest energy levels first.