who is discovered the oxygen?

Answer 1

While, indeed, Michał Sędziwój first wrote about oxygen.

A Swedish person named Carl Wilhelm Scheele was a little more scientific in his description and used scientific methods. But, he did not published his findings until after the discovery of Oxygen by Joseph Priestley. Priestley published his discovery, consequently Priestley is usually given the credit.

Get an "A".

Answer 2

Michał Sędziwój

Answer 3

The one that the world remembers is Joseph Priestley:
http://en.wikipedia.org/wiki/Joseph_Priestley