Meitnerium

Meitnerium, ₁₀₉Mt
Meitnerium
Pronunciation	/maɪtˈnɪəriəm/ ⓘ; (myte-NEER-ee-əm); /ˈmaɪtnəriəm/ ⓘ; (MYTE-nər-ee-əm);
Mass number	[278] (data not decisive)
Meitnerium in the periodic table
	hassium ← meitnerium → darmstadtium
Atomic number (Z)	109
Group	group 9
Period	period 7
Block	d-block
Electron configuration	[Rn] 5f14 6d7 7s2 (predicted)
Electrons per shell	2, 8, 18, 32, 32, 15, 2 (predicted)
Physical properties
Phase at STP	solid (predicted)
Density (near r.t.)	27–28 g/cm3 (predicted)
Atomic properties
Oxidation states	common: (none); (+1), (+3), (+6)
Ionization energies	1st: 800 kJ/mol ; 2nd: 1820 kJ/mol ; 3rd: 2900 kJ/mol ; (more) (all estimated);
Atomic radius	empirical: 128 pm (predicted)
Covalent radius	129 pm (estimated)
Other properties
Natural occurrence	synthetic
Crystal structure	face-centered cubic (fcc) ; (predicted)
Magnetic ordering	paramagnetic (predicted)
CAS Number	54038-01-6
History
Naming	after Lise Meitner
Discovery	Gesellschaft für Schwerionenforschung (1982)
Isotopes of meitnerium

Meitnerium is a synthetic chemical element; it has symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature, but can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 4.5 seconds, although the unconfirmed meitnerium-282 may have a longer half-life of 67 seconds. The element was first synthesized in August 1982 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, and it was named after Lise Meitner in 1997.

In the periodic table, meitnerium 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 yet been carried out to confirm that it behaves as the heavier homologue to iridium in group 9 as the seventh member of the 6d series of transition metals. Meitnerium is calculated to have properties similar to its lighter homologues, cobalt, rhodium, and iridium.