What is Selenium? Electron configuration, Atomic Number & Mass, Uses

What is Selenium?

Selenium is a chemical element that is numbered 34 in the Periodic Table of the Elements. It is located in the fourth period of the VI group of the main (A) subgroup of the Periodic Table.

Electronic Configuration of Selenium-

The selenium atom consists of a positively charged nucleus (+34), inside which there are 34 protons and 45 neutrons, and around 34 electrons move in three orbits.

Below you will get all the information related to Selenium electron configuration-

Se- 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁴

Short notation of electronic configuration of Selenium:

Se-[Ar]3d¹⁰4s²4p⁴

The selenium atom and Br⁺¹ , Kr+2 have the same electronic configuration.

The order of filling the shells of a selenium (Se) atom with electrons: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p.

On the 's' sublevel there can be up to 2 electrons, on the 's' - up to 6, on the 'd' - up to 10 and on the 'f' up to 14.

Selenium has 34 electrons, we fill the electron shells in the order described above:

• 2 electrons on the 1s-sublevel
• 2 electrons on the 2s-sublevel
• 6 electrons in the 2p sublevel
• 2 electrons in the 3s-sublevel
• 6 electrons in the 3p sublevel
• 2 electrons on the 4s-sublevel
• 10 electrons on the 3d sublevel
• 4 electrons in the 4p-sublevel

Discovery of Selenium (Se)-

In 1817 Selenium element was discovered by Swedish chemist Jons Jacob Berzelius and his assistant Johann Gottlieb Gahn. The name of element 34, selenium, is formed from Selene which designates the Greek goddess of the Moon.

In 1817 Berzelius and Gahn discovered that the process of making sulfuric acid from pyrite results in a residue. This residue is in the form of a precipitate with red and brown tints. Berzelius analyzes it and realizes that when it is heated, the sample emits a slight odor of "radish" associated with tellurium.

This metal being rare and precious, he continued his analysis and realized that he was discovering a new element having chemical properties very close to those of tellurium but which differed slightly from it. Berzelius then proposes naming it selenium.

So we can say Selenium (Se) name was proposed by its discoverer after finding that its properties were very close to those of tellurium (Te), which it was associated with almost systematically in natural minerals.

Thus, its name was chosen on the same basis as the name tellurium derived from tellus, a Greek term for the Earth. It seemed logical to Berzelius to name this new element in reference to the companion of our planet.

Presence of Se in its natural state

Selenium is a common element, we can even say that it is 50 times more common than tellurium even if it is 4,000 times less present than sulfur. In fact, selenium has a clarity equal to 0.1 ppm.

Selenium, when native, replaces sulfur in mineral compositions such as:

• Seleniferous pyrite
• Lead, iron, copper and zinc selenides
• And crooksite, with the CuThSe formula

In addition, selenium is present in plants, grains, herbs or yeasts because it is able to concentrate there at the risk of being high or toxic. When this is the case, there may be impairments harmful to health but also to well-being.

Physical and chemical properties of Selenium-

Selenium as a single body

• Pure selenium (Se), when it is in its crystalline form, is at room temperature a black solid although it has different allotropic forms such as the amorphous form, that is to say in the form of powder, and can then have a red or blue color.
• Selenium also shows semiconductor properties, used in particular to manufacture transistors found in computers and cell phones.
• Element 34 is an element capable of reacting with most acids. It can burn with oxygen to form selenium dioxide, with the formula SeO 2 and also combines with different metals to form selenides.

Selenium ions in aqueous solution

• The selenite ion, with the formula SeO₃ ^2- , is a toxic polyatomic anion, the conjugate base of selenious acid.
• The selenate ion, of formula SeO₄ ^2- , is a polyatomic anion, the conjugate base of selenic acid.

Selenium-based compounds

• Lead selenide (PbSe) is a naturally occurring mineral also called clausthalite.
• Selenium sulfide (SeS2) is an antiseborrheic active ingredient that is found in some shampoos.
• Zinc selenide (formula ZSe) is a yellow-orange solid semiconductor used in some diodes.
• Selenium dioxide(SeO2) is a white solid which can be formed by combustion of pure selenium in oxygen. It can be added to glasses to give them a red color.

Isotopes of Selenium (Se)

Element 34, Selenium, is a chemical element that has 29 isotopes with a mass number between 65 and 94.In addition to these isotopes, selenium also has 9 nuclear isomers, in which only 5 are stable:

• Selenium 74
• Selenium 76
• Selenium 77
• Selenium 78
• And selenium 80

Uses of Selenium (Se)

Below are the uses of Selenium element-

• Selenium is used in photocopiers and laser printers, more specifically in drums.
• Selenium can be used to improve the qualities of copper and steel, which will be tanned through the application of selenious acid as is the case with firearms.
• Selenium is used to manufacture solar batteries and quantum dots due to its semiconductor properties.
• Cadmium red, a dye for glass and plastics, is actually cadmium sulfoselenide.

Toxicity of Selenium Element

Overexposure to selenium can be toxic. This overexposure can cause dizziness, fatigue but also irritation of various mucous membranes, while too little selenium consumption can cause heart and muscle problems. In some cases, selenium poisoning is so severe that it can even be fatal.

Ecotoxicity of Selenium (Se)

Selenium in itself is not a toxic agent but human activities can increase its concentration in soil, groundwater and surface water.

What is most dangerous in the environment with selenium are its reactions with other chemical elements present in nature because it can accumulate in organisms and contaminate an entire food web.

FAQs

What is the atomic number of Selenium?

We denote Selenium as SE and the atomic number of Selenium is 34.

What is the atomic mass of Selenium?

The atomic mass of Selenium is 78.96 u.

What is the atomic valency of Selenium?

The valencyof selenium characterizes the ability of the Se atom to form chemical bonds. Selenium atoms in compounds show valency VI, IV, II, I.

What are the oxidation states of Se?

Selenium atoms in compounds have oxidation states 6, 4, 2, 1, -2.

What are Selenium ions?

Se⁶⁺, Se⁴⁺, Se²⁺ , Se¹⁺ , Se^2- , Se⁰ are Selenium ions.

Know about more periodic elements- Gadolinium, Germanium, Neon, Oxygen, Potassium, Promethium, Selenium, Sodium, Terbium, Tellurium, Yttrium, Ytterbium, Zirconium