Cesium (Cs) Electron Configuration(Explained for Beginners)

Cesium is an alkali metal having an atomic mass of 132.90 u and belongs in the s-block of the periodic table. Let us discuss the electronic configuration of Cs.

Cs is the soft, flexible metal among all the group 1 elements. It is pale gold in color and due to the presence of 6s orbital, it shows a relativistic effect. The 137-Cs is radioactive in nature having 30 years of half-life.

Cs have less affinity towards electrons due to alkali metal and possess positive charge. In this article, we learn more details about the electronic configuration of Cesium like ground state configuration, orbital diagram, and condensed electronic configuration in the following section.

1. How to write the Cesium electron configuration

Cs is the sixth-period element of group 1 so it has a total of 55 electrons and those electrons can be arranged properly in a particular orbital having a particular principle number by three rules,

Step 1- we write the shell number as per the principle quantum number is the primary step which is arranged by the increasing order of energy as per the Aufbau principle.
It is shown that Cesium has six electronic shells.
Step 2- we should include the subshell or orbital followed by the next step.
There are four orbitals s, p, d, and f which can occupy the electrons for Cs.
Step 3 – we put the respective number of electrons for each orbital as superscript by their shell number as per Hund’s rule.
Step 4 – we follow Pauling’s exclusion principle for the opposite pairing of electrons in each orbital and get the full electronic configuration of Cs.

2. Cesium electron configuration diagram

Now we draw the electronic configuration diagram of Cs which has 55 electrons and those electrons are fitted in the diagram by the above three rules and we draw the diagram following way,

First, 1s will be filled by an electron as it has lower energy and it has one orbital, and each orbital consists maximum of two electrons with opposite spin.
After 1s, 2s orbital will be filled by two electrons as per energy order
After 2s, the 2p orbital will be filled as per energy order and it has three orbitals so it can accumulate a maximum of six electrons.
After 2p, the 3s orbital is filled by two electrons as per higher energy than the previous one.
After 3s, the 3p orbital will be filled by six electrons as it has three orbitals and more energy.
After 3p, the 4s orbital will be filled by two electrons as it has higher energy for a higher principle quantum number.
After 4s, the 3d orbital will be filled due to effective nuclear charge and shielding effect it has higher energy than 4s and the d orbital has five subshells so it can accumulate a maximum of ten electrons.
After 3d, the 4p orbital will be filled by six electrons.
After 4p, the 5s orbital is filled by two electrons as per energy.
After 5s, the 4d orbital is filled by a maximum of ten electrons as it has more energy than 5s.
After 4d, the 5p orbital is filled by the six electrons.
After 5p, the 6s orbital is filled by one electron only due to the availability of the valence electrons of Cs.

So, the diagram will be –

Screenshot 2022 11 17 142537 — **Electronic Diagram of Cesium**

3. Cesium electron configuration notation

Cesium electronic configuration notation is depicted as follows-

[Xe]6s¹,

Cs electronic configuration notation consists of 55 electrons and out of 55 electrons 54 are taken from the Xenon noble gas configuration and the remaining one electron is placed in 6s orbital, where 6 is the principle quantum number and s is the valence orbital where 1 is the number of electron present.

4. Cesium unabbreviated electron configuration

The unabbreviated electronic configuration of Cesium is, 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶6s¹. It consists of a total of 55 electrons which are filled as follows –

Two electrons are present in 1s orbital.
Two electrons in 2s orbital.
Six electrons in 2p orbital.
Two electrons in 3s orbital.
six electrons in 3p orbital.
Ten electrons in 3d orbital.
Two electrons in 4s orbital.
Six electrons in 4p orbital.
Ten electrons in 4d orbital.
Two electrons in 5s orbital.
Six electrons in 5p orbital.
One electron in 6s orbital.

5. Ground state Cesium electron configuration

The ground state electronic configuration of Cesium is 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶6s¹ where all the electrons will be placed in proper orbital with 0 energy level.

Screenshot 2022 11 16 170303 — Ground State electronic
Configuration of Cs

6. Excited state of Cesium electron configuration

Excited state configuration of Cesiumwill be, 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁵6s². we consider the first excited state where paired electrons of lower energized orbital move to the orbital having higher energy, and here one electron from 5p moves to the 6s orbital, but the total electrons will remain same.

Screenshot 2022 11 16 170337 1 — Excited State electronic
Configuration of Cs

7. Ground state Cesium orbital diagram

The cesium ground state orbital diagram is the number of electrons present per shell around the nucleus

K -shell = containing two electrons (1s¹)
L-shell = containing 8 electrons (2s²2p⁶)
M-shell = containing 18 electrons (3s²3p⁶3d¹⁰)
N-shell = containing remaining 27 electrons (4s²4p⁶4d¹⁰5s²5p⁶5d¹⁰6s¹)
The orbital diagram of Cesium will be-

Screenshot 2022 11 16 170349 — **Cesium Orbital Diagram**

8. Cs⁺ electron configuration

The electronic configuration of Cs⁺ will be 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁶ or [Xe] because it adopts a noble gas configuration similar to 54 electrons. Where Cs⁺ is the mono-cationic form of Cesium where one electron is removed from its 6s orbital.

9. Cs²⁺ electron configuration

The electronic configuration of Cs²⁺ will be 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰5s²5p⁵. Where in the diatomic form Cs it loses two more electrons one from 6s and another one from full-filled 5p orbital and the number of electrons present in Cs²⁺ is 53.

10. Cs condensed electron configuration

The condensed electronic configuration of Cs is [2 8 18 25] which is the electronic shell of Cs and the presence of the number of electrons per shell.

Conclusion

Cesium is the heavier alkali metal in the stable form, where the first ionization energy of Cs is very low because upon releasing one electron it will be more stable by adopting a noble gas configuration. The 2^nd ionization energy of Cs is very high due to the removal of an electron from a filled 5p orbital.

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Biswarup Chandra Dey

Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.