[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a radioactive salt of the metal cobalt. Cobalt chloride Co-57 is a radiopharmaceutical used in nuclear medicine as an imaging agent in the diagnosis of certain forms of cancer."}, {"from": "gpt", "value": "[Cl-1].[Cl-1].[57Co+2]"}]