Final answer:
Oxygen, with an atomic number of 8, always has 8 protons, defining the element. Its isotopes, 16O, 17O, and 18O, differ by the number of neutrons, with 8, 9, and 10 neutrons respectively. All isotopes of oxygen possess 6 valence electrons and are stable with natural abundances specific to each isotope.
Step-by-step explanation:
Oxygen has an atomic number of 8, which defines the number of protons in an oxygen atom. Therefore, the answer to how many protons oxygen has is 8.
Oxygen has three stable isotopes: 16O, 17O, and 18O. The atomic number (the number of protons) for all these isotopes is still 8, which is a characteristic feature of all oxygen isotopes. However, the difference in the isotopes lies in their number of neutrons. The mass number of an isotope, represented by the superscript in the isotope notation, is the sum of protons and neutrons. By subtracting the number of protons from the mass number, we find that 16O has 8 neutrons (16-8), 17O has 9 neutrons (17-8), and 18O has 10 neutrons (18-8).
As for valence electrons, oxygen has a total of 6. Regarding the isotopes, their natural abundance is 99.76% for 16O, 0.20% for 18O, and 0.04% for 17O. Isotopes that are unstable and decay are known as radioisotopes; however, these three isotopes of oxygen are stable.