zero

Explanation: Oxygen atoms have 8 protons and 8 electrons. By adding two electrons to the second energy level, a more stable noble gas electron configuration is achieved by the oxygen. Since no protons are added the overall charge is -2.

Because electrons have a charge of 1-, adding two electrons would make the charge of the oxide ion 2-. Oxygen takes the electron density from other atoms when it forms two bonds, to become a negative two ion.

That make the charge experienced by the eighth electron in the second shell equal to (9-2-½(7))=3.5 positive charges. That is sufficient to hold that eighth electron in the second shell. An oxygen nucleus has 8 protons and 8 neutrons. There are two electrons in the first shell.

Gas

Oxygen Exhibits High Reactivity Due to its electronegativity, oxygen forms stable chemical bonds with almost all elements to give the corresponding oxides.

Oxygen is the chemical element with the symbol O and atomic number 8. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2.

The tetraoxygen molecule (O4), also called oxozone, was first predicted in 1924 by Gilbert N. Lewis, who proposed it as an explanation for the failure of liquid oxygen to obey Curie’s law.

Due to the known distribution of O2 and therefore also O4, O4 slant column densities can be used to retrieve aerosol profiles which can then be used again in radiative transfer models to model light paths.

Trioxygen

Neutral oxides show neither basic nor acidic properties and hence do not form salts when reacted with acids or bases, e.g., carbon monoxide (CO); nitrous oxide (N2O); nitric oxide (NO), etc., are neutral oxides.

Calcium oxide (CaO) , is a metal oxide. Like other metal oxides it is a basic oxide because it dissolves in water to form calcium hydroxide.

Na2O is basic oxide whereas Cl2O7 is acidic oxide.