how many isotopes of oxygen occur naturally on earth
Isotopes of oxygen Naturally occurring oxygen is composed of three stable isotopes, 16O, 17O, and 18O, with 16O being the most abundant (99.762% natural abundance). Depending on the terrestrial source, the standard atomic weight varies within the range of [15.99903, 15.99977] (the conventional value is 15.999). Known oxygen isotopes range in mass number from 12 to 24.