Meitnerium
. Meitnerium, symbol Mt, chemical element with atomic number 109. It is produced artificially by nuclear fusion (in which a chemical element with larger atoms is produced by fusing together smaller atoms from other elements). Each meitnerium atom has a very large nucleus, or central mass, containing positively charged particles called protons and neutral particles called neutrons . The large number of particles in the nucleus makes the atom unstable and causes the atom to split apart into smaller components soon after it is created. The International Union of Pure and Applied Chemistry named element 109 meitnerium (Mt), which was previously called unnilennium, to honor Austrian Swedish physicist Lise Meitner , a pioneer in the field of nuclear fission (the splitting of atomic nuclei). Meitnerium has the atomic number 109, which means that each Mt atom contains 109 protons in the nucleus. Scientists have created several isotopes of meitnerium, or forms of the element that contain dif