Electronic data		Thermal data		Steric data
Shells: 2,8,18,23,8,2 Orbitals: [Xe] 4f5 6s2 Electronegativity: 1.1, -- 1. Ionization potential: 5.55 eV 2. Ionization potential: 10.903 eV 3. Ionization potential: 22.283 eV Oxidation states: 3 Electrical conductivity: --		Melting point: 1042 °C Boiling point: 3000 °C (estimated) Specific heat: 0.18 J/gK Heat of fusion: -- kJ/mol Heat of vaporization: -- kJ/mol Thermal conductivity: 0.179 W/cmK		Atomic radius: 2.62 Å Ionic radius: 1.09 Å () Covalent radius: 1.63 Å Atomic volume: 22.39 cm³/mol Density (293 K): 6.475 g/cm³ Crystal structure: Hexagonal

Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
143Pm	0	142.911	5/2	265y	EC	View
144Pm	0	144	5	360y	EC	View
145Pm	0	144.913	5/2	17.7y	EC,	View
146Pm	0	146	3	5.53y	EC,-	View
147Pm	0	146.915	7/2	2.62y	-	View
148Pm	0	148	1	5.37d	-	View
148Pmm	0	148	6	41.3d	-,IT	View
149Pm	0	149	7/2	2.212d	-	View
151Pm	0	151	5/2	1.183d	-	View

Legend

Name origin:	Named for the Greek god, Prometheus.
Description:	Rare earth metal of synthetic origin on the earth, naturally made in stars.
Discovered by:	J.A. Marinsky, L.E. Glendenin, C.D. Coryell
Year:	1945
Place:	United States
Sources:	Does not occur naturally. Found among fission products of uranium, thorium, and plutonium.
Use(s):	It has been used as a source of radioactivity for thickness-measuring gages.