   the chalcogens () are the chemical elements in group 16 of the periodic table. this group is also known as the oxygen family. it consists of the elements oxygen (o), sulfur (s), selenium (se), tellurium (te), and the radioactive element polonium (po). the synthetic element livermorium (lv) is predicted to be a chalcogen as well. often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. the word "chalcogen" is derived from a combination of the greek word khalkÏs (ÏÎ±Î»ÎºÏÏ) principally meaning copper (the term was also used for bronze/brass, any metal in the poetic sense, ore or coin), and the latinised greek word genÄs, meaning born or produced.  sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. all of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. their most common oxidation states are â2, +2, +4, and +6. they have relatively low atomic radii, especially the lighter ones. lighter chalcogens are typically nontoxic in their elemental form, and are often critical to life, while the heavier chalcogens are typically toxic. all of the chalcogens have some role in biological functions, either as a nutrient or a toxin. the lighter chalcogens, such as oxygen and sulfur, are rarely toxic and usually helpful in their pure form. seleni
Chalcogens Groups_in_the_periodic_table Periodic_table