Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 55

Oxygen exists as . An oxide ion is an oxygen atom with a 2− charge, so it has 2 extra electrons compared to a neutral oxygen atom. Therefore: oxygen contains 8 protons (due to the mass number) and 8 neutrons (due to the difference between the mass number and the atomic number); and, because it has a 2− charge, it has to contain 2 more electrons than it has protons (because each electron has a negative charge), so it has 10 electrons.

Remember from the previous chapter that an ion is an atom or a group of atoms that has a charge.