Nobelium, chemical element, symbol No; for physical constants see Periodic Table. Nobelium was discovered by Albert Ghiorso and his coworkers at the Lawrence Radiation Laboratory in Berkeley, Calif., in 1958. A target of curium isotopes was bombarded with carbon-12 ions in a heavy-ion linear accelerator (HILAC) to produce nobelium-254. It is a metallic element and a member of the actinide series. Eleven radioactive isotopes of nobelium are now known. Nobelium-259, an alphaemitter with a half-life of 58 minutes, is the most stable.