Final answer:
A neutral atom of oxygen has 8 protons and 8 electrons. When oxygen becomes an anion by gaining two electrons, it has 10 electrons. Stable isotopes of oxygen vary in neutron count but have the same number of protons and electrons in a neutral state.
Step-by-step explanation:
A neutral atom of oxygen, which has an atomic number of 8, will have the same number of electrons as it does protons, in order to maintain a neutral charge. So, a neutral oxygen atom has 8 protons and 8 electrons.
Atoms become ions by gaining or losing electrons. For example, oxygen can gain two electrons to become an oxide anion represented as O²⁻, with 8 protons, 8 neutrons, and 10 electrons. The atomic number determines the number of protons (Z), and in a neutral atom, the number of protons equals the number of electrons.
In contrast, isotopes of oxygen have the same number of protons but different numbers of neutrons. For example, three stable isotopes of oxygen exist: 16O, 17O, and 18O, indicating variations in their neutron count but with a consistent proton and electron count in their neutral state.