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] 3d10 4s2 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 3d10 4s2 4p4. 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 3d10 4s2 4p4, 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
Selenium electron configuration

Selenium electron configuration notation

The Se electron configuration is [Ar] 3d10 4s2 4p4.

Selenium unabbreviated electron configuration

The unabbreviated electron configuration of Se is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4.

Ground state selenium electron configuration

The electron configuration of the Se atom in the ground state will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px2 4py1 4pz1. The last 4 electrons of the 4p orbitals are located in the three orbitals such as px, py, and pz in which the px orbital has 2 electrons. Then py and pz 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 3d10 4s2 4px1 4py1 4pz1 4dxy1. The Se atom absorbs energy, resulting in one electron present in the 4px orbital jump to the d orbitals of 4dxy.

Ground state selenium orbital diagram

The ground state electron configuration of the Se atom will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4px2 4py1 4pz1. 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, 4px, 4py and 4pz having 4 electrons. The 4py and 4pz orbital is singly occupied. Then 4px orbital gets doubly occupied.
Ground state selenium orbital diagram
Ground state selenium orbital diagram

Selenium condensed electron configuration

The condensed electron configuration of Se is [Ar] 3d10 4s2 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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