Selenium Electron Configuration:7 (Easy Step-by-Step Guide)

Selenium is a non-metal element that is classified as a chalcogen. Let us study the electronic configuration of Selenium in detail.

The electron configuration of Selenium is [Ar] 3d¹⁰4s² 4p⁴. The number of electrons per shell of the Selenium atom is 2, 8, 18, 6. The atomic number of Selenium is 34. It has the chemical symbol “Se” and is found in period-4 and group-16 of the periodic table.

In this article, we will study the electron configuration of the Se atom, unabbreviated electron configuration, ground state, and excited state electron configurations.

How to write selenium electron configuration?

The electron configuration of the selenium is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p⁴. Se atom contains a total of 34 electrons. Let us discuss the steps for writing the electron configuration of the Se atom in detail.

Se atom has 4 electronic shells expressed by the principal quantum number (n= 1,2,3 and 4).
K, L, M, and N are the shell’s names, subdivided into sub-energy levels known as s, p, d and f.
The maximum number of electrons that can hold in the s orbital is 2. Similarly, p, d and f sub-shells can hold 6, 10 and 14 respectively.
The sub-energy levels depend on the azimuthal quantum number (l).
The electrons are filled into the orbitals through the Aufbau principle, Pauli’s exclusion principle, and Hund’s rule.
1s orbital of the Se atom has to fill two electrons first, according to the Aufbau principle.
In the second orbit, 8 electrons enter into the 2s and 2p orbitals of the L shell.
The 18 electrons must fill in the 3s, 3p and 3d orbitals.
The third orbital is now full. So, the remaining 6 electrons will enter the fourth orbit.
The method of entering into the orbitals is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p⁴, the electronic configuration of the selenium atom.

Selenium electron configuration diagram

The method of distribution of the electrons in the orbitals of the Se atom is followed by the 2 important points are

The orbital, which has minimum energy has to fill first. Therefore, the electrons are filled from a lower to a higher energy level.
A fixed number of electrons are present in each orbital, followed by 2n² electrons.

Selenium electron configuration notation

The Se electron configuration is [Ar] 3d¹⁰4s² 4p⁴.

Selenium unabbreviated electron configuration

The unabbreviated electron configuration of Se is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p⁴.

Ground state selenium electron configuration

The electron configuration of the Se atom in the ground state will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p_x² 4p_y¹ 4p_z¹. The last 4 electrons of the 4p orbitals are located in the three orbitals such as p_x, p_y, and p_z in which the p_x orbital has 2 electrons. Then p_y and p_z orbital has 1 electron each.

Excited state of selenium electron configuration

The electron configuration of the Se atom in the excited state is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p_x¹ 4p_y¹ 4p_z¹4d_xy¹. The Se atom absorbs energy, resulting in one electron present in the 4p_x orbital jump to the d orbitals of 4d_xy.

Ground state selenium orbital diagram

The ground state electron configuration of the Se atom will be 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰4s²4p_x² 4p_y¹ 4p_z¹. These 34 electrons are arranged in increasing order. The orbital diagram of the Se atom is shown below.

The electrons are filled in orbitals from lower to higher energy levels in the order of 1s< 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d, and so on.
s, p, d and f subshell consists of 1, 3, 5, and 7 orbitals, respectively.
Each orbital gets one electron first, then start pairing as per Hund’s rule.
The 4p orbit has 3 orbitals, 4p_x, 4p_y and 4p_z having 4 electrons. The 4p_y and 4p_z orbital is singly occupied. Then 4p_x orbital gets doubly occupied.

**Ground state selenium orbital diagram**

Selenium condensed electron configuration

The condensed electron configuration of Se is [Ar] 3d¹⁰4s² 4p⁴.

Conclusion:

Selenium has the property to form various types of allotropes. Crystalline hexagonal Selenium is the most stable allotropes of it. It forms several rings, which are converted into more stable chains. Se atoms have 7 natural isotopes and several synthetic isotopes as well.

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Supriya Upadhya

Hi….I am Supriya Upadhya, a Post Graduate in Organic chemistry with good understanding of Chemistry concepts and worked as Junior research fellow in synthesis of anti cancer agent. Also worked on Anti-Microbial Polymer synthesis as part of Post graduate thesis.