Question

What is the s, p, d, f configuration of iron?

Answer 1

The electrons are arranged in a specific manner in an atom. This arrangement is called an electronic configuration. The s, p, d, and f are the subshells and orbitals present in the atoms, the electron resides in these orbitals.

Complete answer:
Iron is present in the fourth row of the periodic table, the sixth column of the transition metals, i.e. d block. The atomic number of iron is $26$ , that indicates the presence of $26$ electrons in one neutral atom of iron. Now, these electrons are arranged in a specific manner inside the atom.
The core orbital of iron contains a similar configuration as that of Argon (Ar), i.e. $\;1s,2s,2p(3),3s\;\& 3p(3)$ .
The valence orbital of iron contains $4s\& 3d(3)$ . (The numbers in parentheses represent the number of orbitals).
For writing the electron configuration, we only need the valence orbitals, and we can omit the core orbitals by representing it using the configuration of noble gas Argon, i.e. $[Ar]$ instead of $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}$ . If we count the superscripts and sum them up we will get $18$ , which means the remaining eight electrons will be present in the valence orbital.
Finally, the 4s orbitals are higher in energy than 3d orbitals by about 3.75 eV when they are partially filled like this, so we write the 3d before the 4s. Thus, the electronic configuration will be $[Ar]3{d^6}4{s^2}$ .
The expanded form will be - $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^6}4{s^2}$ .

Note:
It should be noted that the sequence of orbital in electronic configuration must follow Aufbau principle. The sequence should not be tampered and the number of electrons should be written as superscript while the numbers written before s, p, d, and f indicate the shell number.