All of the chalcogens have some role in biological functions, either as a nutrient or a toxin.
Oxygen is generally extracted from air and sulfur is extracted from oil and
natural gas. Selenium and tellurium are produced as byproducts of copper
refining. Polonium and livermorium are most available in particle accelerators.
The primary use of elemental oxygen is in steelmaking. Sulfur is mostly
converted into sulfuric acid, which is heavily used in the chemical industry.
Selenium's most common application is glassmaking. Tellurium compounds are
mostly used in optical disks, electronic devices, and solar cells. Some of
polonium's applications are due to its radioactivity.
The Group 6A is the one where there are observed variations of properties of the elements.
For example, Polonium is a metal, tellurium is a metalloid and selenium, sulfur and oxygen are nonmetals.
Though, there are like properties, such as: all the elements form oxygen-compounds and sodium-compounds.
In the Group 6A the 2nd and 3rd period elements have different structures: oxygen has an allotrope (O3) and sulfur has many allotropes.
Sulfur, tellurium and selenium are also called chalcogens because they are found in copper ores (khalkos is the Greek name of copper).
Sulfur is also known as the "burning stone" and the sulfur compounds are smelling and poisonous. The well known H2SO4 is an important compound of sulfur.
Sulfur and selenium are important elements in human diet.