Symbol	Pm
Atomic number	61
Group	-
Period	6
Block	f
Classification	Lanthanide

Appearance	Metallic
Color	Silver

Number of protons	61 p+
Number of neutrons	84 n0
Number of electrons	61 e-

From Wikipedia, the free encyclopediaPromethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.

Phase at STP	Solid
Density	7.26 g/cm3
Atomic weight	145 u

Melting point	1315 K 1041.85 °C 1907.33 °F
Boiling point	3273 K 2999.85 °C 5431.73 °F
Heat of vaporization	289 kJ/mol

Electronegativity (Pauling Scale)	1.13
Electron affinity	12.45 kJ/mol
Oxidation states	+2, +3 (a mildly basic oxide)
Ionization energies	540 kJ/mol 1050 kJ/mol 2150 kJ/mol 3970 kJ/mol

Electron configuration Shorthand configuration	[Xe] 4f5 6s2
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2
Electrons per shell	2, 8, 18, 23, 8, 2
Valence electrons	2
Valency electrons	3
Bohr model	Figure: Shell diagram of Promethium (Pm) atom.
Orbital Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 6s

Discovery	Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin (1945)
Named by	Grace Mary Coryell (1945)
Discovery of promethium 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 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 generally 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.

CAS Number	7440-12-2
ChemSpider ID	22386
EC number	231-121-9
PubChem CID Number	23944