Which oxygen isotopes occur naturally?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — oxygen group element Modern version of the periodic table of the elements (printable).

Natural oxygen consists of a mixture of three stable isotopes:

Oxygen-16: 99.759 percent
Oxygen-17: 0.037 percent
Oxygen-18: 0.204 percent1

While these stable isotopes occur naturally, several radioactive isotopes have been prepared artificially, such as oxygen-15, which is used in scientific research. Variations in the relative abundances of the stable isotopes, particularly the ratio of oxygen-18 to oxygen-16, are used by scientists to study climatic history and biochemical processes.123