Promethium

Kemiallinen merkki: Pm
Järjestysluku: 61
Kategoria: lantanoidit
Ryhmä: n/a
Jakso: 6
Lohko: f
Moolimassa: [145] g/mol
Elektronia kuorilla: 2, 8, 18, 23, 8, 2
CAS-numero: 7440-12-2
Olomuoto: kiinteä
Tiheys: 7,26 kg/l (lähellä huoneenlämpöä)
Sulamispiste: 1315 K (1042 °C, 1908 °F)
Kiehumispiste: 3273 K (3000 °C, 5432 °F)
Kiderakenne: hexagonal
Hapetusluvut: 3
Elektronegatiivisuus: 1,13 (Pauling-asteikko)
Nimen alkuperä: Prometheus
Nimen tarkoitus: the Titan, in Greek mythology, who stole the fire from Mount Olympus and brought it down to mankind - the name was suggested by the discoverer's wife, who felt that they were stealing fire from the gods
Faktoja:
- is notable for being the only other exclusively radioactive element besides technetium which is followed by chemical elements that have stable isotopes
- its longest lived isotope 145Pm is a soft beta emitter with a half-life of 17,7 years"
- does not emit gamma rays, but beta particles impinging on elements of high atomic numbers can generate X-rays
- exists in two allotropic forms, and its chemistry is similar to other lantanidit
- promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity
- is used as a beta radiation source for thickness gauges, in a nuclear battery and in the future, portable X-ray sources
- can be formed in nature as a product of spontaneous fission of uranium-238 and alpha decay of europium-151
- it was calculated that the equilibrium mass of promethium in the Earth's crust is about 560 g due to uranium fission and about 12 g due to the recently observed alpha decay of europium-151