Oxygen atom has the atomic number 8, meaning it has 8 protons and 8 electrons. The electrons in an atom are arranged in shells around the nucleus, and the outermost shell is called the valence shell. In oxygen, the valence shell can hold up to 8 electrons.

But in a neutral oxygen atom, the valence shell has only 6 electrons. Therefore, there are 6 electrons present outside the nucleus of an oxygen atom.