The radioactive isotope cesium-137 was produced in large amounts in fallout from the 1985 nuclear power plant disas-ter at Chernobyl, Ukraine. Write the symbol for this isotope in standard format.

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This results in different atomic masses for the isotopes of the same element. For example, cesium-137 has 55 protons and 82 neutrons, distinguishing it from other isotopes of cesium.

Nuclear notation is a way of representing isotopes using the element's symbol, the mass number, and the atomic number. The mass number is written as a superscript to the left of the element symbol, while the atomic number is written as a subscript. For cesium-137, the notation is represented as ¹³⁷Cs, where 137 is the mass number.

Radioactivity is the process by which unstable atomic nuclei lose energy by emitting radiation. This can occur in the form of alpha particles, beta particles, or gamma rays. Cesium-137 is a radioactive isotope that decays by beta emission, making it significant in discussions of nuclear fallout and environmental impact.