Cobalt Electron Configuration:9 Facts You Should Know!

Cobalt is a chemical element with the symbol Co which is found in the earth’s crust in combined form. Let us discuss the electronic configuration of Cobalt.

The electron configuration of cobalt is 1s22s22p63s23p64s23d7. Cobalt is a very hard, lustrous bluish grey metal that belongs to d-block and is under the category of transition metals. It is a hexagonal closed pack (hcp) crystal structure that is solid in normal conditions and is isolated by the process of smelting.

Cobalt is a versatile and ubiquitous metal because of its varied application. Various oxides, halides, coordination complexes, and organometallic complexes of cobalt are discovered and used. Let us throw light on its electronic factors like configuration, orbital diagrams, etc. 

How to write cobalt electron configuration?

The electron configuration of Co can be written in certain steps.

  • The atomic number of Co is 27 which implies that there are 27 electrons in cobalt. This is significant to write electron configuration.
  • The electron configuration is written by following Aufbau principle and considering the n+l rule for energy.
  • The convention of writing electron configuration is followed that is writing of energy shell first followed by the orbital and then electron in superscript.
  • Keeping in mind the quantum numbers the electron configuration of cobalt is 1s22s22p63s23p64s23d7.

Cobalt electron configuration diagram

The atomic number of cobalt is 27 which implies it has 27 electrons. The electronic configuration of Co diagrammatically is:

  • The first orbital is 1s which can hold 2 electrons (1s2).
  • The second orbital is 2s which again has 2 electrons (2s2).
  • The third orbital has the same energy shell and can withhold 6 electrons (2p6).
  • Next, there will be a new energy shell that has a maximum capacity of 2 electrons (3s2).
  • After 3s2 there is a new orbital that can hold 6 electrons (3p6).
  • Following the n+l rule now there will be a filling of 4s first due to low energy (4s2).
  • Completing the electron count and fulfilling the energy considerations now there will be filling of 3d orbital (3d7).
cobalt electron configuration
Cobalt electron configuration according to Aufbau principle

Cobalt electron configuration notation

The electron configuration notation of Co is:


Here Ar is designated as a noble gas argon configuration which is up to 18 electrons. The rest of the configuration is written afterward following Aufbau’s n+l rule. 

Cobalt unabbreviated electron configuration

The unabbreviated electron configuration of Co is:


Ground state cobalt electron configuration

The ground state electronic configuration of Co is:


Ground state electronic configuration of cobalt

The excited state of cobalt electron configuration

The excited state electron configuration of Co depends upon the type of complexation it is undergoing with ligands, hybridization, and symmetry. In the case of Co1+ ion coordinated to ligands with possible octahedral symmetry, there will be a splitting of ground state energy levels into eg and t2g set.

Ground state cobalt orbital diagram

The ground state Co orbital diagram is 2, 8, 15, 2 which is a broader representation of the electron configuration involving only energy levels following the octet rule or K, L, M, N rule.

Cobalt orbital diagram

Cobalt 3+ electron configuration

The electron configuration of the Co3+ ion is:


Usually, it is expected that electrons will be removed from the same subshell but in the case of Co3+ 1 electrons are removed from 4s and 2 electrons are removed from the 3d orbital. This leads to a half-filled configuration thereby maintaining ion stability.

Cobalt 2+ electron configuration

The electron configuration of the Co2+ ion is depicted as:


In Co2+ there will be the removal of 2 electrons which will be easily removed from 4s orbital thereby removing the whole energy level.


Concluding the article that cobalt is a crucial element in every aspect is it dietary or in coordination chemistry. Due to its electronic configuration, it can be used in the complexation with various ligands which in turn reflects different types of electronic changes it undergoes.

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