Symbol Se/td>
Atomic Number 34
Atomic Mass 30.974
Discovered by  Jöns Jacob Berzelius,

Chemical Properties Of Selenium

Group 16   Melting point 44.15°C, 111.47°F, 317.3 K
Period 4 Boiling point 280.5°C, 536.9°F, 553.7 K  
Block p Density (g cm−3) 1.823 (white)
Atomic number 16 Relative atomic mass 30.974   
State at 20°C Solid Key isotopes 31P
Electron configuration [Ar] 3d104s24p4 CAS number 7723-14-0  
ChemSpider ID 4885617 ChemSpider is a free chemical structure database

What is Selenium?

  • Selenium is a chemical element that is placed in the oxygen group of the periodic table. It is often found in combination with metals like mercury, copper, silver or lead. It is combined with the physical properties of elements like tellurium and sulfur. This element is rare and composed of 90 parts per billion of the Earth crust. It’s a non-metallic chemical element which is a member of the group 16 of the periodic table.
  • This element appears in different allotropic forms of which the most popular are – red amorphous powder, a gray crystalline metal, and a red crystalline material, which is known as a metallic selenium. This gray crystalline form conducts electricity much better in the light than in the dark and can be easily used in photocells. It burns in air and is unaffected by water and dissolves in concentrated nitric acid and alkalis.

Uses Of Selenium

  • It serves as a decolorizer when incorporated in small amounts into the glass. When in large quantity, it imparts to glass a useful clear red color in signal lights. It is also used in preparing red enamels for steel and ceramics. And, for vulcanization of rubber to increase resistance to abrasion.Its electrical resistivity of selenium varies over a great range that depends on variables like temperature & pressure, nature of the allotrope, impurities and the method of refining. Most of the metals are insoluble in this element and the impurities of a non-metallic increase the resistivity.

Practise This Question

The structure of the compound that gives a tribromo derivative with bromine water is: