O2

[Oleanda]

Why is oxygen referred to as O2?

[bhg481]

Because a molecule of oxygen comprises 2 atoms.

[bobbinwales]

Did alot of this at night school back in the day. Oxygen is usually in the O₂ molecule but can be in the form of ozone, thats O₃ You can get the element on its own as O (separate oxygen atom's) but my recolection is that its unstable on earth so dosn't remain, tho it is O in space where its atomic oxygen.

[Peter Pedant]

what level are you at?
O2 is the molecule, and Bobo has pointed out that another molecule is O3 referred to as ozone

oneof my 'hard' question to the Chem master Mr Serra, was what was the difference between 2O and O2
and he said "one is two atoms of oxygen (unstable and doesnt exist on earth) and the second is a molecule of oxygen which is stable"

But you are right - why O2 when carbon is not C and sulphur S8 - or Helium He.

//oh-too// seems like a strongly bound. we are in linguistics now. as we have C-oh-too and N-oh too.