Oxygen was discovered by:
(A) Priestley
(B) Scheele
(C) Boyle
(D) Cavendish

Hint: Oxygen is the chemical element with the atomic number 8 and has a symbol O. In 1772, it was discovered by heating potassium nitrate, mercuric oxide and many other substances.

Complete step by step solution :
- Oxygen was discovered by Scheele. The process of discovery of oxygen is as follows.
Oxygen was discovered about 1772 by Swedish chemist, Carl William Scheele, who obtained it by heating potassium nitrate, mercuric oxide, and many other substances. An English chemist, Joseph Priestley, independently discovered oxygen in 1774 by the thermal decomposition of mercuric oxide and published the findings in the same year.
- Oxygen is interpreted to play a remarkable role in the process of respiration as well as combustion. Further notifications were made that oxygen has the tendency to form acids by combining with many different substances and accordingly names the element as oxygen, which in Greek means ‘acid former’.
Therefore, the correct answer is Option B.

Additional Information: At 46 percent of the mass, oxygen is the most plentiful element in Earth’s crust. The proportion of oxygen by volume in the atmosphere is 21 percent and by weight in seawater is 89 percent.
During respiration, animals and some bacteria take oxygen from the atmosphere and return to it carbon dioxide, whereas by photosynthesis, green plants assimilate carbon dioxide in the presence of sunlight and evolve free oxygen.

Note: Oxygen has two allotropic forms, diatomic and triatomic. The properties of diatomic form suggest that six electron bonds the atoms and two electrons remain unpaired, accounting for the paramagnetism of oxygen.