Oxygen-The History

Oxygen was produced in many experiments conducted by scientists like Robert Hooke, Ole Borche, Mikhail Lomonosov and Pierre Bayen. But none of them realized that Oxygen was an element.Oxygen was first discovered by Swedish pharmacist Carl Wilhelm Scheele. He produced Oxygen gas by heating Mercuric-oxide and various nitrates. 

Carl Wilhelm Scheele

Scheele named Oxygen "Fire Air" because it was the only combustible gas then known to exist. He wrote a manuscript on account of his discovery that he titled "Treatise on Air and Fire". 
He sent the manuscript to his publisher in 1775. But the document was not published till 1777.

"Treatise on Air and Fire"
By Carl  Wilhelm Scheele

In the meantime, A British clergyman Joseph Priestley conducted an experiment regarding the production of a gas on August 1, 1774. He noted that the gas that he produced could make the candle burn brighter. It could also make a mouse be more active and live longer. He also noticed that this gas filled his lungs with an odd full sensation.
Later during 1777, Lavoisier first discovered that Oxygen was an element. First the gas was named "vital air".
But later, Lavoisier named "Vital Air" Oxygene in 1777. And that's how Oxygen entered the English language.