Editing Chalcogen (section)

===Early discoveries===
<!--Not supported by its article: [[File:Greekfire-madridskylitzes1.jpg|thumb|Greek fire, an early sulfur-related discovery]]-->
Sulfur has been known since [[ancient world|ancient times]] and is mentioned in the [[Bible]] fifteen times. It was known to the [[ancient Greeks]] and commonly mined by the [[ancient Romans]]. <!--Not supported by the article: It was also historically used as a component of [[Greek fire]].--> In the Middle Ages, it was a key part of [[alchemy|alchemical]] experiments. In the 1700s and 1800s, scientists [[Joseph Louis Gay-Lussac]] and [[Louis-Jacques Thénard]] proved sulfur to be a chemical element.<ref name="ReferenceB"/>

Early attempts to separate oxygen from air were hampered by the fact that air was thought of as a single element up to the 17th and 18th centuries. [[Robert Hooke]], [[Mikhail Lomonosov]], [[Ole Borch]], and [[Pierre Bayden]] all successfully created oxygen, but did not realize it at the time. Oxygen was discovered by [[Joseph Priestley]] in 1774 when he focused sunlight on a sample of [[mercuric oxide]] and collected the resulting gas. [[Carl Wilhelm Scheele]] had also created oxygen in 1771 by the same method, but Scheele did not publish his results until 1777.<ref name="ReferenceB"/>

Tellurium was first discovered in 1783 by [[Franz Joseph Müller von Reichenstein]]. He discovered tellurium in a sample of what is now known as calaverite. Müller assumed at first that the sample was pure antimony, but tests he ran on the sample did not agree with this. Muller then guessed that the sample was [[bismuth sulfide]], but tests confirmed that the sample was not that. For some years, Muller pondered the problem. Eventually he realized that the sample was gold bonded with an unknown element. In 1796, Müller sent part of the sample to the German chemist [[Martin Klaproth]], who purified the undiscovered element. Klaproth decided to call the element tellurium after the Latin word for earth.<ref name="ReferenceB"/>

Selenium was discovered in 1817 by [[Jöns Jacob Berzelius]]. Berzelius noticed a reddish-brown sediment at a sulfuric acid manufacturing plant. The sample was thought to contain arsenic. Berzelius initially thought that the sediment contained tellurium, but came to realize that it also contained a new element, which he named selenium after the Greek moon goddess Selene.<ref name="ReferenceB"/><ref>{{cite journal|last = Trofast|first = Jan|url = http://www.iupac.org/publications/ci/2011/3305/5_trofast.html|title = Berzelius' Discovery of Selenium|journal= Chemistry International|volume=33 |issue=5|date=September–October 2011 |access-date=November 25, 2013}}</ref>