[{"from": "human", "value": "Describe this molecule. [Ra]"}, {"from": "gpt", "value": "The molecule is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it readily oxidizes on exposure to air, turning black. Radium is an alkaline earth metal that is formed when uranium and thorium break down in the environment. It is extremely radioactive. Radium-226 is the most stable isotope, has a half-life of 1602 years, and decays into radon gas. Radium has been used as a radiation source for treating cancer, in radiography of metals, and combined with other metals as a neutron source for research and radiation instrument calibration. Until the 1960s, radium was a component of the luminous paints used for watch and clock dials, instrument panels in airplanes, military instruments, and compasses. (L991, L1835)"}]