A neutral atom of oxygen-18 has 8 electrons. This is because the atomic number of oxygen is 8, which indicates that it has 8 protons and, in a neutral state, the number of electrons equals the number of protons.
Oxygen-18 is an isotope of oxygen, meaning it has the same number of protons (8) but a different number of neutrons. In the case of oxygen-18, it has 10 neutrons (18 total nucleons – 8 protons = 10 neutrons). However, the number of electrons in a neutral atom remains unchanged and is determined solely by the atomic number.