Oxygen atoms refer to individual units or particles that make up oxygen, a chemical element found in nature. Oxygen is essential for life and is required by most organisms to survive. It makes up about 21% of Earth's atmosphere and is present in many compounds such as water, carbon dioxide, and other substances. The phrase "oxygen atoms" refers specifically to the individual molecules or particles that make up oxygen gas (O2), liquid oxygen (LOX), or solid oxygen (SO2).