Polonium is a rare and highly radioactive element with the symbol Po and atomic number 84. Discovered by Marie Curie and her husband Pierre Curie in 1898, it is known for its intense radioactivity and is primarily used in nuclear applications and as a heat source in space equipment. This element occurs naturally in trace amounts in uranium ores and is produced artificially in nuclear reactors. Due to its toxicity and radioactivity, polonium must be handled with extreme caution. Its most notable use was in the assassination of Alexander Litvinenko, highlighting its dangerous potential.