Chem Explorers

Unraveling the Properties and Applications of Selenium

Selenium is a chemical element that forms part of the chalcogen group on the periodic table. It has the symbol Se and atomic number 34.

Selenium is a brittle, lustrous metallic gray in appearance and has a hexagonal crystalline structure. It was discovered in 1817 by Jns Jacob Berzelius and serves various purposes, including medicinal, electrical, and photographic applications.

In this article, we will discuss the electron configuration of selenium and its properties.

Selenium Electronic Configuration

The electron configuration of selenium pertains to the arrangement of electrons of its 34 electrons. These electrons are distributed among the different energy levels of seleniums atomic structure.

The Aufbau principle states that electrons fill the lowest available energy level before filling higher ones. The electrons also follow Paulis exclusion principle, which states that no two electrons in an atom can have the same set of four quantum numbers.

Hence, there are three orbitals, and 6 electrons are organized into them. Hunds rule states that electrons will occupy if there are two or more orbitals with the same energy level.

Thus, three spin up electrons occupy three different orbitals of the same energy level, and one spin down electron fills the fourth orbital of the same level. The atomic number of selenium is 34, so there are 34 electrons in the atom.

Thus, the electron configuration for Selenium is written as [Ar] 3d^10 4s^2 4p^4.

Selenium Unabbreviated Electron Configuration

The unabbreviated electron configuration of selenium is a less condensed version of the electronic configuration. It allows the viewer to observe each configuration by skip listing the noble gas before the electron configuration.

Hence, the unabbreviated electron configuration for Selenium is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4.

Ground State Selenium Electron Configuration

The ground state electron configuration of selenium is the arrangement of electrons when all the electrons have the lowest energy possible. The electronic configuration of the ground state of selenium is given by the Aufbau principle.

It is [Ar] 3d^10 4s^2 4p^4.

Excited State of Selenium Electron Configuration

The excited state electron configuration refers to the arrangement of electrons location when some of the electrons in the atom have energy levels higher than necessary. These electrons will be excited by some external source like heat or radiation.

The excited state electronic configuration for selenium would be the same as the ground state, except some electrons would be in a higher level than the ground state.

Selenium Condensed Electron Configuration

The condensed electron configuration of selenium, also known as the shortcut notation, is written using a noble gas configuration to represent the core electron configuration of the element. Noble gasses are used because these core electrons are unreactive and do not participate in the chemical reactions of the element.

Hence the condensed electronic configuration would be [Ar] 3d^10 4s^2 4p^4 for selenium.

Allotropes of Selenium

Selenium has three allotropes, crystalline hexagonal Selenium, ring form, and chain form. The most stable allotrope of selenium is Crystalline hexagonal Selenium, also called gray selenium, forms a metallic gray semi-conductive crystal that is widely used in the electronic industry.

The ring form element has cyclic Se8 molecules which form a stable octatomic molecule with a crown shape. The chain form of the element is rather unique as selenium has an infinite snake-like chain of Se atoms bound to one another and is known as red selenium.

Selenium Isotopes

Selenium has 6 stable isotopes and 34 unstable isotopes; Hence, it has over 40 known isotopes. Natural selenium comprises six isotopes, with respective abundances of 49.89% (Se-80), 23.7% (Se-82), 9.58% (Se-76), 8.73% (Se-77), 0.89% (Se-74), and 0.02% (Se-78).

Selenium isotopes have a range of half-lives. Synthetic isotopes are produced via nuclear reactors and particle accelerators.


From the configuration of selenium to its various allotropes and isotopes, selenium is an incredibly versatile element used in various applications, including electronic and medicinal fields. Knowing the electron configuration, stable allotropes, and isotopes provide insight into how selenium behaves during chemical reactions and various other applications in its elemental and complex states.

The properties of selenium are significant in the field of chemistry and some aspects of physics. By knowing how selenium behaves under various circumstances and understanding its properties, developments in the fields where the element is used will continue to advance.

Selenium is a versatile chemical element with properties ranging from its electron configuration, stable allotropes, and isotopes. The electron configuration explains its arrangement of electrons, following the Aufbau principle, Hunds rule, and Paulis exclusion principle.

Selenium has three allotropes, including Crystalline hexagonal Selenium, ring form, and chain form, and multiple stable and unstable isotopes. Knowing the electronic configuration and understanding the stable allotropes, and isotopes is significant in various fields, including the electronic and medicinal industry.

A better understanding of the properties of selenium is crucial in the field of chemistry and few aspects of physics. Providing a comprehensive answer to some frequently asked questions regarding the different aspects of selenium, its behavior, properties, and areas of application underscores its importance to the scientific world and the need for continued advances.


What is the electron configuration of selenium? The electron configuration for Selenium is [Ar] 3d^10 4s^2 4p^4.

What is the difference between the unabbreviated electron configuration and the condensed electron configuration of selenium? The unabbreviated electron configuration for Selenium is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^4, while the condensed electronic configuration for selenium is [Ar] 3d^10 4s^2 4p^4.

What are the allotropes of selenium? Selenium has three allotropes: crystalline hexagonal Selenium, ring form, and chain form.

How many isotopes does Selenium have, and what are they? Selenium has six natural isotopes and over 40 isotopes in total.

The six natural isotopes are Se-80, Se-82, Se-76, Se-77, Se-74, and Se-78. What are the uses of selenium?

Selenium has various industrial and medical applications, including use in electronic devices, as a catalyst in chemical reactions, and in medication to treat cancer and other diseases.

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