Iron (Fe) has atomic number of 26 and it belongs to 4th period and 8th group in the periodic table.

Iron is situated in d-block of the periodic table and it’s one of the most commonly found element in the earth crust

In this article, I will explain to you how you can figure out electronic configuration of iron.

Also, I will be discussing the steps that you need to follow in order to write the electronic configuration of iron.

But firstly, let’s discuss what’s electronic configuration of an element.

Electronic configuration is arrangement of electrons in the atomic orbitals. It shows the number of the electrons present in different orbitals of an atom.

There are two ways to write electronic configuration of an atom (for sure I will be discussing both of these ways here in this article).

First method is to write it in terms of orbitals and second method is to write it using Bohr’s Atomic Model of atom.

In first method, we need to write the configuration in terms of subshells and orbitals. For example, in an atom there are subshells called 1s, 2s, 3s, 3p etc. And also these subshells have orbitals in them and each orbital can contain at least two electrons. All the subshells of type s have just one orbital while all the subshells of type p have three orbitals in them and we need to follow Aufbau’s Principle for filling up electrons in different orbitals.

In Bohr models approach, we need to consider that atom is made up of different orbits/energy levels which are called KLMN.

Name of atom | Iron |

Atomic Symbol | Fe |

Number of electrons | 26 |

Number of electrons per shell | 2, 8, 14, 2 |

Orbital electron configuration | 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2} |

Valence electrons | 8 |

Valency | 2 or 3 |

## Writing electron configuration of Iron (Fe)

### Understanding Aufbau’s Principle

Electron configuration of iron can be written using Aufbau Principle.

In simple words, there are commonly four different types of subshells which are s, p, d and f.

These subshells can hold a maximum number of electrons on the basis of formula 2(2I + 1).

In this formula I is azimuthal quantum number.

Subshell | Angular Momentum Number (I) | Number of Orbitals in Subshell (2l + 1) | Maximum Electrons Subshell can hold 2(2l + 1) |
---|---|---|---|

s | 0 | 1 | 2 |

p | 1 | 3 | 6 |

d | 2 | 5 | 10 |

f | 3 | 7 | 14 |

- s subshell can hold maximum of two electrons
- p Sub shell can hold maximum six electrons
- d Subshell can hold maximum of 10 electrons
- f can hold maximum 14 electrons

As I have discussed above of Aufbau Principle It’s all about filling of orbitals in increasing order of their energy.

So let’s see the formula which we can use to figure out the energy of an orbital.

According to Aufbau Principle

Energy of an orbital = n + I

where n is principle Quantum Number

I is azimuthal quantum number

Lower the value of n + i for an orbital less energy it has as compared to an orbital which have higher value of n + i

So let’s now see the values of **n + I** for different orbitals in an atom.

Orbital | Value of n | Value of I | Value of n plus i |
---|---|---|---|

1s | 1 | 0 | 1 |

2s | 2 | 0 | 2 |

3s | 3 | 0 | 3 |

3p | 3 | 1 | 4 |

3d | 3 | 2 | 5 |

4s | 4 | 0 | 4 |

4p | 4 | 1 | 5 |

4d | 4 | 2 | 6 |

4f | 4 | 3 | 7 |

### Orbitals Energy Levels Diagram

Therefore, according to above values of n + I for different orbitals we can make a sequence of orbitals in increasing order of their energies 1s 2s 2p 3s 3p 4s 3d 4p 5s and so on.

This is the sequence that we need to follow in order to figure out electron configuration of iron.

But wait a minute. Do you need to remember this sequence? 🙄

Actually? No, you can just use the diagram given below.

In the below diagram, you need to start feeling of orbitals from top left corner and move along the arrows.

So let’s now write electron configuration of iron and do remember that iron in total have **26 electrons**. So we need to fill all these 26 electrons in different orbitals as per sequence of orbitals which we figured out above using Aufbau Principle.

### Filling up 26 electrons in Orbitals of Iron

Writing electron configuration of iron | Orbital | Electrons Left (26 total electrons) |
---|---|---|

First two electrons will go into 1s orbital | 1s^{2} | 26 – 2 = 24 |

Next two electrons will go into 2s orbital | 2s^{2} | 24 – 2 = 22 |

Next six electrons will go into 2p orbitals | 2p^{6} | 22 – 6 = 16 |

Next two electrons will go into 3s orbital | 3s^{2} | 16 – 2 = 14 |

Next six electrons will go into 3p orbital | 3p^{6} | 14 – 6 = 8 |

Next two electrons will go into 4s orbital | 4s^{2} | 8 – 2 = 6 |

Remaining all eight electrons will go into 3d orbitals | 3d^{6} | 6 – 6 = 0 |

### Writing Electron Configuration of Iron

Summarising all this we get electron configuration of iron is **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{6}**

But its an electron configuration writing rule that we need to write all orbitals which have same principle quantum number together.

Therefore electron configuration of iron can also be written as **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}**.

Moreover we can also write electron configuration of iron in terms of its nearest noble gas which is Argon. Therefore we can replace **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6}** with [Ar]

Where [Ar] represents electron configuration of noble gas Argon.

So electron configuration of iron in terms of noble gas Argon can be written as

**[Ar] 3d**

^{6}4s^{2}## Bohr Model Electron Configuration of Iron (Also called KLMN electron configuration)

Niels Bohr, a Danish scientist, was the first to propose the concept of an orbit around an atom. In 1913, he presented a model of the atom to the scientific community. As per this model, the electrons in an atom follow a set path as they go around the nucleus in circular motion.

These set paths are called “Orbits” and are numbered as 1, 2, 3, ……… depending upon their closeness to nucleus of atom. So first circular path around nucleus is numbered as 1, second as 2 and so no. Moreover orbits are also denoted by English letters.

- First orbit – K and have n = 1
- Second orbit – L and have n = 2
- Third orbit – M and have n = 3
- Fourth orbit – N and have n = 4
- and so on.

How many electrons any of these orbits can hold is determined by using formula 2n^{2} where n is number of orbit. Based upon this formula, different orbits in the atom can hold electrons as following.

- First orbit – K (n = 1) can hold 2n
^{2}= 2 (1)^{2}= 2 electrons - Second orbit – L and have n = 2 can hold 2n
^{2}= 2 (2)^{2}= 2 (4) = 8 electrons - Third orbit – M and have n = 3 can hold 2n
^{2}= 2 (3)^{2}= 2 (9) = 18 electrons - Fourth orbit – N and have n = 4 can hold 2n
^{2}= 2 (4)^{2}= 2 (16) = 32 electrons - and so on.

But really hard to figure out how many electrons will be in each orbit of iron just based upon the fact that first orbit can have 2 electrons, second can have 8 electrons and so on.

So better way to figure out orbit electron configuration of iron is to just look at it’s orbital electron configuration which we figured out above and use that to figure out orbit electron configuration of iron.

Above we have figured out electron configuration of iron is **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 4s^{2} 3d^{6}**

Let’s sum together the electrons which are in same principle quantum number orbital.

Orbital | Orbit | Total Electrons |
---|---|---|

1s^{2} | K | 2 |

2s^{2}2p ^{6} | L | 8 |

3s^{2}3p ^{6}3d ^{6} | M | 14 |

4s^{2} | N | 2 |

**As Iron atom have total 26 electrons, therefore its Orbit Electron Configuration is two electrons in K orbit, 8 electrons in L orbit, fourteen electrons in M orbit and two electrons in L orbit.**

## Summary

Iron atom in total have 26 electrons, to write down the electron configuration of iron, the first two electrons would go into the 1s orbital. Because the 1s orbital can only accommodate two electrons, next two electrons are placed in the 2s orbital, next 6 electrons are placed in 2p orbital. Out of 16 remaining electrons, 2 would go into 3s orbital, 6 electrons are placed in 3p orbitals, two are placed in 4s orbital and remaining 6 electrons are placed in 3d orbital. Putting all this together, electron configuration of iron is **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}**. Which can also be written as

**[Ar] 3d**where [Ar] represents electron configuration of noble gas Argon.

^{6}4s^{2}As Iron atom have total 26 electrons, therefore its Orbit Electron Configuration is two electrons in K orbit, 8 electrons in L orbit, fourteen electrons in M orbit and two electrons in L orbit.

## FAQs

**What is electron configuration of neutral Iron (Fe)?**

Neutral iron atom means that it have equal number of electrons and protons. As in neutral state iron atom have total 26 electrons, therefore it’s electron configuration is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}.

Which means iron atom have 2 electrons each in its 1s, 2s orbitals, 6 electrons in 2p orbitals, 2 electrons in 3s orbital, six electrons in 3p orbital, 6 electrons in 3d orbital and two electrons in 4s orbital.

**What is electron configuration of ground-state Iron (Fe) atom?**

Ground state atom means that all electrons inside it are in least possible energy state levels, therefore net total energy of atom in ground-state is minimum out of all states of it. As iron atom just have 26 electrons, therefore it’s electron configuration is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}. Which means iron atom have 2 electrons each in its 1s, 2s orbitals, 6 electrons in 2p orbitals, 2 electrons in 3s orbital, 6 electrons in 3p orbital, 6 electrons in 3d orbital and 2 electrons in 4s orbital.

**How many unpaired electrons are there in ground state of Iron (Fe)?**

Ground state atom means that all electrons inside it are in least possible energy state levels, therefore net total energy of atom in ground-state is minimum out of all states of it. As iron atom just have 26 electrons, therefore it’s electron configuration is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}.

As is clear from the electron configuration all the orbitals are fully filled except 3d orbitals.

Out of five 3d orbitals, one is fully filled with two electrons and other four have one electron each.

Therefore **iron have just four unpaired electron.**

**What is Valency of Iron?**

Iron usually combines with other elements by loosing either 2 or 3 electrons.**Therefore valency of iron is 2 or 3.**

**Which element have electron configuration 1s**

^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{6}4s^{2}?Iron (Fe)

**In what type of orbital is the outermost electron in Iron (Fe) atom?**

Electron configuration of iron is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}

From this it can be clearly observed that outermost electron in iron atom is present in **4s orbital**.

**How many electron shells does Iron have?**

Iron have electron configuration 2, 8, 14, 2 which means it have 2 electrons in K shell, 8 electrons in L shell, 14 electrons in M shell and two electrons in N shell. Therefore iron have **4 electron shells**.

**How many energy levels does Iron have?**

Iron have electron configuration 2, 8, 14, 2 which means it have 2 electrons in K shell, 8 electrons in L shell, 13 electrons in M shell and 2 electrons in L shell.

Another name for shells is energy levels, because shells just represent different energy states of electrons, therefore in total **Iron have 4 energy levels** which are K, L, M and N.

**How many orbitals are in Iron?**

Electron Configuration of iron atom is **1s ^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2}**

1s have 1 orbital

2s have 1 orbital

2p have 3 orbitals

3s have 1 orbital

3p have 3 orbitals

3d have 5 orbitals

4s have 1 orbital

Summing all this together we get 1 + 1 + 3 + 1 + 3 + 5 + 1 = 15 orbitals.

Therefore in total

**iron atom have 15 orbitals**.

**What is Electron Configuration of Fe**

^{2+}?Fe^{2+} is formed when an Fe atom looses 2 electrons.

Electron configuration of Fe is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2} and if two electrons are removed then Fe will change into Fe^{2+} and electron configuration will become 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6}.

Therefore **electron configuration of Fe ^{2+} is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6}**.

**What is Electron Configuration of Fe**

^{3+}?Fe^{3+} is formed when an Fe atom looses 3 electrons.

Electron configuration of Fe is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{6} 4s^{2} and if three electrons are removed then Fe will change into Fe^{3+} and electron configuration will become 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{5}.

Therefore **electron configuration of Fe ^{3+} is 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} 3d^{5}**.