Q. Fe orbital diagram.

Step 1: Identify the atomic number

Iron, \( \mathrm{Fe} \), has atomic number \(26\). That means it has \(26\) electrons.

Step 2: Write the electron configuration in order of filling (Aufbau principle)

Electrons fill orbitals in increasing energy order:
\(1s, 2s, 2p, 3s, 3p, 4s, 3d\).

For iron:

\[
\mathrm{Fe}: \ 1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^6\ 4s^2\ 3d^6
\]

Step 3: Convert the configuration into subshell box (orbital) diagrams

Each orbital box holds at most \(2\) electrons with opposite spins.

Here are the filled orbitals:

\(1s\) (filled with 2 electrons)

\[
1s:\ \uparrow\downarrow
\]

\(2s\) (filled with 2 electrons)

\[
2s:\ \uparrow\downarrow
\]

\(2p\) (3 orbitals, total 6 electrons → all filled)

\[
2p:\
\begin{matrix}
\uparrow\downarrow & \uparrow\downarrow & \uparrow\downarrow
\end{matrix}
\]

\(3s\) (filled with 2 electrons)

\[
3s:\ \uparrow\downarrow
\]

\(3p\) (3 orbitals, total 6 electrons → all filled)

\[
3p:\
\begin{matrix}
\uparrow\downarrow & \uparrow\downarrow & \uparrow\downarrow
\end{matrix}
\]

\(4s\) (filled with 2 electrons)

\[
4s:\ \uparrow\downarrow
\]

\(3d\) (5 orbitals, total 6 electrons)

First place one electron in each \(3d\) orbital (Hund’s rule), then add the 6th electron to complete pairing in the next available orbital.

\(3d\) has 5 boxes:

\[
3d:\
\begin{matrix}
\uparrow\downarrow & \uparrow & \uparrow & \uparrow & \uparrow
\end{matrix}
\]

Step 4: Final orbital occupancy summary (most important part is \(4s\) and \(3d\))

The key result for iron is:

• \(4s^2\)
• \(3d^6\)

Full orbital filling can be summarized as:

\[
\mathrm{Fe}:\ 1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,4s^2\,3d^6
\]