Iron Electron Configuration and Atomic Orbital Diagram
Iron is the 26th element in the periodic table and the symbol is ‘Fe’. Iron has an atomic number of 26, which means that its atom has 26 electrons around its nucleus.
The electron configuration for iron is 1s2 2s2 2p6 3s2 3p6 4s2 3d6 which means that the first two electrons enter the 1s orbital. Since the 1s orbital can hold only two electrons, the next two will enter the 2s orbital. The next six electrons enter the 2p subshell. The p subshell can hold a maximum of six electrons. So first we put six electrons in the 2p subshell and then the next two electrons in the 3s orbital.
Since the 3s is now full, the electrons will move to the 3p subshell, where the next six electrons will enter. The 3p subshell is now full. Consequently, the following two electrons will enter the 4s orbital. Since the 4s orbital is now full, the remaining six electrons will move into the 3d subshell. Hence, the electron configuration of iron will be 1s2 2s2 2p6 3s2 3p6 4s2 3d6.
The electron configuration of iron refers to the arrangement of electrons in the iron atom’s orbitals. It describes how electrons are distributed among the various atomic orbitals and energy levels, and provides a detailed map of where each electron is likely to be found.
To understand the mechanism of iron electron configuration, you need to understand two basic things. These are orbits and orbitals. Also, you can arrange electrons in those two ways. In this article, I have discussed all the necessary points to understand the mechanism of iron electron configuration including Fe²⁺ and Fe³⁺ ions, orbital diagrams, valency and valence electrons, and ground and excited state configurations. I hope this will be helpful in your study.
Electron arrangement of Iron through Bohr Model
Scientist Niels Bohr was the first to give an idea of the atom’s orbit. He provided a model of the atom in 1913 and provided a complete idea of orbit in that model.
The electrons of the atom revolve around the nucleus in a certain circular path. These circular paths are called orbits (shells or energy levels). These orbits are expressed by n. [n = 1,2,3,4 . . . The serial number of the orbit]
The name of the first orbit is K, L is the second, M is the third, and N is the name of the fourth orbit. The electron holding capacity of each orbit is 2n2.
| Shell Number (n) | Shell Name | Electrons Holding Capacity (2n2) |
| 1 | K | 2 |
| 2 | L | 8 |
| 3 | M | 18 |
| 4 | N | 32 |
Explanation:
- Let, n = 1 for K orbit. So, the maximum electron holding capacity in the K orbit is 2n2 = 2 × 12 = 2 electrons.
- n = 2, for L orbit. The maximum electron holding capacity in the L orbit is 2n2 = 2 × 22 = 8 electrons.
- n=3 for M orbit. The maximum electron holding capacity in the M orbit is 2n2 = 2 × 32 = 18 electrons.
- n=4 for N orbit. The maximum electron holding capacity in N orbit is 2n2 = 2 × 42 = 32 electrons.
Therefore, the maximum electron holding capacity in the first shell is two, the second shell is eight and the 3rd shell can have a maximum of eighteen electrons.
The atomic number is the number of electrons in that element. The atomic number of iron is 26. That is, the number of electrons in iron is twenty-six. Therefore, the iron atom will have two electrons in the first shell and eight in the 2nd shell.
According to Bohr’s formula, the third orbit will have sixteen electrons but the third orbit of iron will have fourteen electrons and the remaining two electrons will be in the fourth orbit. Therefore, the order of the number of electrons in each shell of the iron atom is 2, 8, 14, 2.
The Bohr atomic model has many limitations. In the Bohr atomic model, the electrons can only be arranged in different shells but the exact position, orbital shape, and spin of the electron cannot be determined.
Also, electrons can be arranged correctly from 1 to 18 elements. The electron arrangement of any element with atomic number greater than 18 cannot be accurately determined by the Bohr atomic model following the 2n2 formula. We can overcome all limitations of the Bohr model following the electron configuration through orbital.
Electron configuration of Iron through Aufbau Model
Atomic energy shells are subdivided into sub-energy levels. These sub-energy levels are also called orbital. The most probable region of electron rotation around the nucleus is called the orbital.
The sub-energy levels depend on the azimuthal quantum number. It is expressed by ‘l’. The value of ‘l’ is from 0 to (n – 1). The sub-energy levels are known as s, p, d, and f.
| Orbit Number | Value of ‘l’ | Number of subshells | Number of orbitals | Subshell name | Electrons holding capacity | Electron configuration |
| 1 | 0 | 1 | 1 | 1s | 2 | 1s2 |
| 2 | 0 1 | 2 | 1 3 | 2s 2p | 2 6 | 2s2 2p6 |
| 3 | 0 1 2 | 3 | 1 3 5 | 3s 3p 3d | 2 6 10 | 3s2 3p6 3d10 |
| 4 | 0 1 2 3 | 4 | 1 3 5 7 | 4s 4p 4d 4f | 2 6 10 14 | 4s2 4p6 4d10 4f14 |
Explanation:
- If n = 1,
(n – 1) = (1–1) = 0
Therefore, the value of ‘l’ is 0. So, the sub-energy level is 1s. - If n = 2,
(n – 1) = (2–1) = 1.
Therefore, the value of ‘l’ is 0, 1. So, the sub-energy levels are 2s, and 2p. - If n = 3,
(n – 1) = (3–1) = 2.
Therefore, the value of ‘l’ is 0, 1, 2. So, the sub-energy levels are 3s, 3p, and 3d. - If n = 4,
(n – 1) = (4–1) = 3
Therefore, the value of ‘l’ is 0, 1, 2, 3. So, the sub-energy levels are 4s, 4p, 4d, and 4f. - If n = 5,
(n – 1) = (n – 5) = 4.
Therefore, l = 0,1,2,3,4. The number of sub-shells will be 5 but 4s, 4p, 4d, and 4f in these four subshells it is possible to arrange the electrons of all the elements of the periodic table.
| Sub-shell name | Name source | Value of ‘l’ | Value of ‘m’ (0 to ± l) | Number of orbital (2l+1) | Electrons holding capacity 2(2l+1) |
| s | Sharp | 0 | 0 | 1 | 2 |
| p | Principal | 1 | −1, 0, +1 | 3 | 6 |
| d | Diffuse | 2 | −2, −1, 0, +1, +2 | 5 | 10 |
| f | Fundamental | 3 | −3, −2, −1, 0, +1, +2, +3 | 7 | 14 |
The orbital number of the s-subshell is one, three in the p-subshell, five in the d-subshell, and seven in the f-subshell. Each orbital can have a maximum of two electrons.
The sub-energy level ‘s’ can hold a maximum of two electrons, ‘p’ can hold a maximum of six electrons, ‘d’ can hold a maximum of ten electrons, and ‘f’ can hold a maximum of fourteen electrons.
Aufbau is a German word, which means building up. The main proponents of this principle are scientists Niels Bohr and Pauli. The Aufbau method is to do electron configuration through the sub-energy level.
The Aufbau principle is that the electrons present in the atom will first complete the lowest energy orbital and then gradually continue to complete the higher energy orbital.
The energy of an orbital is calculated from the value of the principal quantum number ‘n’ and the azimuthal quantum number ‘l’. The orbital for which the value of (n + l) is lower is the low energy orbital and the electron will enter that orbital first.
| Orbital | Orbit (n) | Azimuthal quantum number (l) | Orbital energy (n + l) |
| 3d | 3 | 2 | 5 |
| 4s | 4 | 0 | 4 |
Here, the energy of 4s orbital is less than that of 3d. So, the electron will enter the 4s orbital first and enter the 3d orbital when the 4s orbital is full. Following the Aufbau principle, the sequence of entry of electrons into orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p.
Therefore, the complete electron configuration for iron should be written as 1s2 2s2 2p6 3s2 3p6 4s2 3d6.
Note: The abbreviated electron configuration of iron is [Ar] 3d6 4s2. When writing an electron configuration, you have to write serially.
How to write the orbital diagram for iron?
Orbital diagrams are usually represented by boxes. Each box represents an orbital and the arrows within the box represent the position of the electron. The boxes are arranged in order of energy of the orbitals.
The lowest energy orbitals are closest to the nucleus and the higher energy orbitals are progressively further away from the nucleus in order of their energy levels. To write the orbital diagram of iron, you have to write the orbital notation of iron. Which has been discussed in detail above.
1s is the closest and lowest energy orbital to the nucleus. Therefore, the electrons will first enter the 1s orbital. According to Hund’s principle, the first electron will enter 1s orbital in the clockwise direction and the next electron will enter the 1s orbital in the anti-clockwise direction.
The 1s orbital is now filled with two electrons. The next two electrons will enter the 2s orbital just like the 1s orbital. The next three electrons will enter the 2p orbital in the clockwise direction and the next three electrons will enter the 2p orbital in the anti-clockwise direction.
The 2p orbital is now full. Then the next two electrons will enter the 3s orbital just like the 1s orbital. Then the next three electrons will enter the 3p orbital in the clockwise direction and the next three electrons will enter the 3p orbital in the anti-clockwise direction.
The 3p orbital is now full. So, the next two electrons will enter the 4s orbital just like the 1s orbital. The 4s orbital is now full. Therefore, the next five electrons will enter the 3d orbital in the clockwise direction and the remaining one electron will enter the 3d orbital in the anti-clockwise direction. This is clearly shown in the figure of the orbital diagram of iron.
Try the Orbital Diagram Calculator and get instant results for any element.
Iron ion(Fe2+, Fe3+) electron configuration
The ground state electron configuration of iron is 1s2 2s2 2p6 3s2 3p6 3d6 4s2. This electron configuration shows that the last shell of iron has two electrons and the d-orbital has a total of six electrons. Therefore, the valence electrons of iron are eight.
There are two types of iron ions. The iron atoms exhibit Fe2+ and Fe3+ ions. The iron atom donates two electrons in the 4s orbital to form an iron ion(Fe2+).
Fe – 2e– → Fe2+
Here, the electron configuration of iron ion(Fe2+) is 1s2 2s2 2p6 3s2 3p6 3d6. The iron atom donates two electrons in 4s orbital and an electron in 3d orbital to convert iron ion(Fe3+).
Fe – 3e– → Fe3+
The electron configuration of iron ion(Fe3+) is 1s2 2s2 2p6 3s2 3p6 3d6. Iron atom exhibit +2 and +3 oxidation states. The oxidation state of the element changes depending on the bond formation.
This post really helped clarify the electron configuration of iron for me! The diagrams made it much easier to visualize the concept of atomic orbitals. I particularly appreciated the detailed explanation of how the electron filling order works. Thank you for making such a complex topic accessible!
This post on iron’s electron configuration and atomic orbital diagram was incredibly insightful! The detailed explanation about the distribution of electrons and the significance of each orbital really helped clarify some concepts I’ve struggled with. Thank you for making such complex topics more accessible!
This post on iron’s electron configuration and atomic orbital diagram was incredibly informative! I appreciate the clear breakdown of the configurations and how it relates to the periodic table. It really helped solidify my understanding of how electron arrangements influence the properties of elements. Thanks for sharing!
This post does a fantastic job breaking down the complexities of iron’s electron configuration and atomic orbital diagram! The visuals really helped me grasp the concepts better, especially how the orbitals are filled. Thanks for making this topic so accessible!