Selenium Chemical Properties (25 Facts You Should Know)

The periodic table contains various elements among them selenium is one element. Let us discuss the chemical properties of selenium elements.

Selenium shows the non-metallic character. Selenium is present in various food grains especially whole grains and some animal products like fish, eggs, etc. The selenium amount in grains depends on the content of the soil. Selenium element is used in making pigments for paints, plastics, and ceramics.

In this article, we will be learning about the atomic number, atomic weight, electronegativity, symbol, density, ionization energies, magnetism, and many more properties of selenium with some important facts about it.

Selenium symbol

The symbol of the selenium element in the periodic table is ‘Se’. The representation of the chemical elements in the form of alphabetic characters using two to three letters is called a chemical symbol.

Selenium element

Selenium group in the periodic table

The Selenium element occupies a place in the 16th group of the periodic table. It is present after sulfur and before tellurium elements in the 16th group.

Selenium period in the periodic table

The Selenium element occupies the place under the 4th period of the periodic table. It is present after arsenic and before bromine elements in the 4th period.

Selenium block in the periodic table

The Selenium element comes under the p-block elements of the periodic table.

Selenium atomic number

The selenium element has atomic number 34, as it has 34 protons in its nucleus. The proton number of an element is the same as its atomic number.

Selenium Atomic Weight

The atomic weight of the Selenium element is 78.96 u. The usual weight or mass of an element is known as its atomic weight.

Selenium Electronegativity according to Pauling

As per Pauling’s scale, the electronegativity value of the selenium element is 2.55. The element’s ability to attract the electrons from another atom towards itself is known as electronegativity.

Selenium atomic Density

The atomic density of the selenium element is 4.809 gm/cm3. The atomic quantity of an element measured per cubic centimeter or unit volume of a substance is called atomic density.

Selenium melting point

The melting point value of the Selenium element is 220.8 °C (494 K, 429.4°F). The evaluated exact temperature value at which the chemical compound or element starts melting is called its melting point.

Selenium boiling point

The boiling point value of the Selenium element is 685 °C (958 K, 1265 °F).

Selenium Vanderwaals radius

The VanderWaals radius for selenium element is 190 pm.

Selenium ionic/covalent radius

The covalent radius of the selenium element is 120 pm and the ionic radius of the selenium element is 42 pm.

Selenium isotopes

The elements with atoms having the same protons and different neutrons are called isotopes of that element. Let us see below the isotopes of the selenium element.

The selenium element has various stable or unstable isotopes and natural selenium has 34 protons represented as 34Se. Below is the given table that shows the various isotopes of selenium.

Serial no.Isotopes of Selenium elementCharacteristics
1Selenium 74, 76, 77, 78, and 80Most stable isotope of the Selenium element
2Selenium 79 – 79SeIsotope of Selenium element with a half-life period of 1 minute.
3Selenium 72 – 72SeIsotope of Selenium with a half-life value of 8.4 days
4Selenium 75 – 75SeIsotope of Selenium with a half-life value of 114.9 days
5Selenium 80 – 80SeIsotope of Selenium with half-life value of  0.97(5)×1020 y
Isotopes of Selenium

Selenium electronic shell

The atomic orbitals of an element contain electrons in a sequential form known as its electronic shell. Let us see below the electronic shell of the selenium element.

The electronic shell of the selenium element has a sequence of electrons in its atomic orbitals as 2, 8,18, and 6.

Selenium energy of first ionization

The first ionization energy of the selenium element is 940.963 kJ mol‑1.

Selenium energy of second ionization

The second ionization energy value of the selenium element is 2044.52 kJ mol‑1.

Selenium energy of third ionization

The third ionization energy value of the selenium element is 2973.727 kJ mol‑1.

Selenium oxidation states

The oxidation state of selenium atom is −2, −1, 0, +1, +2, +3, +4, +5, and +6 but the -2, +2, +4, and +6 are the most prominent oxidation states of selenium element.

Selenium electron configurations

The electrons in an atom get dispersed in the subshells of its atoms in some precise manner known as the electronic configuration. Let us see the electronic configuration of selenium.

The electronic configuration for the selenium atom is given below:

  • 122s22p63s23p63d104s24p4 or
  • [Ar] 3d104s24p4

Selenium CAS number

The CAS number for the selenium element is 7782-49-2.

Selenium ChemSpider ID

The ChemSpider ID of the selenium atom is 4885617. The overall data of chemical elements delivered by the service of the Royal Society of Chemistry (RSC) with a unique ID is called its ChemSpider ID.

Selenium allotropic forms

The atoms of the same element with a different form of its structure are called the allotropes of that element. Let us see the various allotrophs of selenium elements below.

The selenium element shows three allotropes as follows:

  • Red Se is brittle and lustrous in nature and acts as an insulator.
  • Grey Se is also brittle and glossy and formed due to the heating of red Se. It can act as a semiconductor.
  • Black Se also acts as an insulator.

Selenium chemical classification

The selenium element is classified as a non-metallic element in the periodic table. The non-metallic character of elements is generally shown on the right side of the periodic table. Selenium is present on the right side of p-block elements showing non-metallic character.

Selenium state at room temperature

The Selenium element is a solid element at room temperature.

Is Selenium paramagnetic?

The atoms of elements contain paired or unpaired electrons in their outer orbitals showing paramagnetic or diamagnetic nature. Let us see selenium’s magnetic nature.

The Selenium element is paramagnetic in nature. It contains two unpaired electrons in its outer ‘4p’ subshell. Thus the selenium element has unfilled ‘4p’ orbitals and on the application of an external magnetic field, it gets attracted toward the magnetic field.

Conclusion:

Selenium element has the symbol Se. It has the atomic number 34. It comes under the 15th group, 4th period, and p-block element of the periodic table. Selenium is paramagnetic and has three allotropes as red Se, grey Se, and black Se.

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