Promethium | ||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pronunciation | /proʊˈmiːθiəm/ | |||||||||||||||||||||||||||||
Appearance | metallic | |||||||||||||||||||||||||||||
Mass number | [145] | |||||||||||||||||||||||||||||
Promethium in the periodic table | ||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||
Atomic number (Z) | 61 | |||||||||||||||||||||||||||||
Group | f-block groups (no number) | |||||||||||||||||||||||||||||
Period | period 6 | |||||||||||||||||||||||||||||
Block | f-block | |||||||||||||||||||||||||||||
Electron configuration | [Xe] 4f5 6s2 | |||||||||||||||||||||||||||||
Electrons per shell | 2, 8, 18, 23, 8, 2 | |||||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||||
Phase at STP | solid | |||||||||||||||||||||||||||||
Melting point | 1315 K (1042 °C, 1908 °F) | |||||||||||||||||||||||||||||
Boiling point | 3273 K (3000 °C, 5432 °F) | |||||||||||||||||||||||||||||
Density (at 20° C) | α-145Pm: 7.149 g/cm3 α-147Pm: 7.247 g/cm3 [1] | |||||||||||||||||||||||||||||
Heat of fusion | 7.13 kJ/mol | |||||||||||||||||||||||||||||
Heat of vaporization | 289 kJ/mol | |||||||||||||||||||||||||||||
Atomic properties | ||||||||||||||||||||||||||||||
Oxidation states | +2, +3 (a mildly basic oxide) | |||||||||||||||||||||||||||||
Electronegativity | Pauling scale: 1.13 (?) | |||||||||||||||||||||||||||||
Ionization energies |
| |||||||||||||||||||||||||||||
Atomic radius | empirical: 183 pm | |||||||||||||||||||||||||||||
Covalent radius | 199 pm | |||||||||||||||||||||||||||||
![]() | ||||||||||||||||||||||||||||||
Other properties | ||||||||||||||||||||||||||||||
Natural occurrence | from decay | |||||||||||||||||||||||||||||
Crystal structure | double hexagonal close-packed (dhcp) (hP4) | |||||||||||||||||||||||||||||
Lattice constants | a = 0.36393 pm c = 1.1739 pm (at 20 °C)[1] | |||||||||||||||||||||||||||||
Thermal expansion | 9.0×10−6/K (at r.t.)[2][a] | |||||||||||||||||||||||||||||
Thermal conductivity | 17.9 W/(m⋅K) | |||||||||||||||||||||||||||||
Electrical resistivity | est. 0.75 µΩ⋅m (at r.t.) | |||||||||||||||||||||||||||||
Magnetic ordering | paramagnetic[3] | |||||||||||||||||||||||||||||
Young's modulus | α form: est. 46 GPa | |||||||||||||||||||||||||||||
Shear modulus | α form: est. 18 GPa | |||||||||||||||||||||||||||||
Bulk modulus | α form: est. 33 GPa | |||||||||||||||||||||||||||||
Poisson ratio | α form: est. 0.28 | |||||||||||||||||||||||||||||
CAS Number | 7440-12-2 | |||||||||||||||||||||||||||||
History | ||||||||||||||||||||||||||||||
Discovery | Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin (1945) | |||||||||||||||||||||||||||||
Named by | Grace Mary Coryell (1945) | |||||||||||||||||||||||||||||
Isotopes of promethium | ||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||
Promethium is a chemical element with symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in the Earth's crust at any given time. Promethium is one of the only two radioactive elements that are followed in the periodic table by elements with stable forms, the other being technetium. Chemically, promethium is a lanthanide. Promethium shows only one stable oxidation state of +3.
In 1902 Bohuslav Brauner suggested that there was a then-unknown element with properties intermediate between those of the known elements neodymium (60) and samarium (62); this was confirmed in 1914 by Henry Moseley, who, having measured the atomic numbers of all the elements then known, found that the element with atomic number 61 was missing. In 1926, two groups (one Italian and one American) claimed to have isolated a sample of element 61; both "discoveries" were soon proven to be false. In 1938, during a nuclear experiment conducted at Ohio State University, a few radioactive nuclides were produced that certainly were not radioisotopes of neodymium or samarium, but there was a lack of chemical proof that element 61 was produced, and the discovery was not much recognized. Promethium was first produced and characterized at Oak Ridge National Laboratory in 1945 by the separation and analysis of the fission products of uranium fuel irradiated in a graphite reactor. The discoverers proposed the name "prometheum" (the spelling was subsequently changed), derived from Prometheus, the Titan in Greek mythology who stole fire from Mount Olympus and brought it down to humans, to symbolize "both the daring and the possible misuse of mankind's intellect". However, a sample of the metal was made only in 1963.
The two sources of natural promethium are rare alpha decays of natural europium-151 (producing promethium-147) and spontaneous fission of uranium (various isotopes). Promethium-145 is the most stable promethium isotope, but the only isotope with practical applications is promethium-147, chemical compounds of which are used in luminous paint, atomic batteries and thickness-measurement devices. Because natural promethium is exceedingly scarce, it is typically synthesized by bombarding uranium-235 (enriched uranium) with thermal neutrons to produce promethium-147 as a fission product.
Cite error: There are <ref group=lower-alpha>
tags or {{efn}}
templates on this page, but the references will not show without a {{reflist|group=lower-alpha}}
template or {{notelist}}
template (see the help page).
© MMXXIII Rich X Search. We shall prevail. All rights reserved. Rich X Search