Oxygen is in Group VI and having atomic number of 8. it has a total of 2 electrons in the first shell (or K shell), and 6 electrons in the first shell (or K shell). Hence, it has a valency of 6. When oxygen atom forms a covalent bond with two Hydrogen atoms, it forms water (or H2O.) An oxygen atom contains 8 electrons that revolve around two orbital shells. The first shell, or the inner shell, contains 2 electrons. Whereas, the outer shell contains 6 electrons.