Tom Skerritt. Biography: Tom Skerritt is probably the best-known actor whose name is never remembered. A rugged outdoors type, Skerritt briefly attended Wayne State University and UCLA before making his film bow in [[Feature~V115961~War Hunt~warhunt]] (1962). His...
The chemical formula for oxygen is O2 and for individual oxygen  atom its symbol is O.   Gases such as oxygen exist as diatomic molecules.
Oxygen gas is two oxygen atoms bonded together, O 2. Water, is one oxygen atom bonded to two different hydrogen atoms, H 2 O. When atoms are bonded together, (H 2, O 2, H 2 O etc.) we call the total structure a molecule.