Meitnerium is a chemical element with the symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element that can be created in a laboratory but is not found in nature); the most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds. Meitnerium was first created in 1982 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the physicist Lise Meitner.
In the periodic table, it is a d-block transactinide element. It is a member of the 7th period and is placed in the group 9 elements, although no chemical experiments have been carried out to confirm that it behaves as the heavier homologue to iridium in group 9. Meitnerium is calculated to have similar properties to its lighter homologues, cobalt, rhodium, and iridium.
