The ionization energy of an element refers to the amount of energy required to remove an electron from a neutral atom of that element in the gaseous state. Oxygen is commonly found as a diatomic molecule (O₂), so its ionization energy can be described as the energy needed to remove an electron from an oxygen atom in the O₂ molecule.
The ionization energy of oxygen can vary depending on the specific process being considered, such as removing the first, second, or third electron. However, typically, when people refer to the ionization energy of oxygen, they are referring to the first ionization energy, which is the energy required to remove one electron from a neutral oxygen atom in the gas phase.
The first ionization energy of oxygen is approximately 1314 kilojoules per mole (kJ/mol), or 1314 kJ/mol.
The equation representing the first ionization of oxygen can be written as:
O(g) -> O⁺(g) + e⁻
This equation shows that a gaseous oxygen atom (O) loses an electron (e⁻) to form a singly charged oxygen ion (O⁺).