Oxygen isotope ratio cycle likely driven by the Lomagundi carbon isotope excursion. Oxygen isotope ratio cycle Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples, measured with the isotope fractionation. The ratio is linked to water temperature of ancient oceans, which in turn reflects ancient climates. Cycles in the ratio mirror climate changes in geologic history. Oxygen (chemical symbol O) has three naturally occurring isotopes: O, O,
Isotopes of americium Isotopes of americium Americium (Am) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no known stable isotopes. The first isotope to be synthesized was Am in 1944. The artificial element decays into alpha particles. Americium has an atomic number of 95 (the number of protons in the nucleus of the americium atom). Eighteen radioisotopes of americium from Am to Am (with the exception of Am) have been characterized, with the most stable being Am with a half-life of 7,370 years, and Am with a half-life of 432.2 years. All