Oxygen-16 is a stable isotope of the element oxygen, which is essential for life on Earth. It has eight protons and eight neutrons in its nucleus, giving it an atomic mass of approximately 16 atomic mass units (amu). This isotope makes up about 99.76% of all naturally occurring oxygen, making it the most abundant form. Oxygen-16 plays a crucial role in various biological and chemical processes, including respiration and photosynthesis. It is also used in scientific research, such as studying climate change through ice core samples, where the ratio of oxygen isotopes can provide insights into historical temperatures.