Element Promethium

Promethium ElementAll of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth’s crust at any given time.
Promethium is a chemical element with the symbol Pm and atomic number 61.
Promethium is one of 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.
The element’s atomic radius is the second largest among all the lanthanides but is only slightly greater than those of the neighboring elements
Promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements

Names and Identifiers

Chemical Formula:Pm
CAS:7440-12-2
Molecular Weight:145.00000g/mol
EC Number :n/a
MDL Number:n/a
Color:silvery-white/ metallic
Other Names:Prometio, Promécio
PubChem CID:23944
IUPAC Name:Promethium
Inchl:InChI=1S/Pm
InChI Key:VQMWBBYLQSCNPO-UHFFFAOYSA-N
Canonical SMILES:[Pm]
ICSC Number:n/a

Physical & Chemical Properties

Phase:Solid
Density:7.26 g/cm³
Boiling Point:3273 K ​(3000 °C, ​5432 °F)
Melting Point:1315 K ​(1042 °C, ​1908 °F)
Molecular Formula:Pm
Flash Point:n/a
Exact Mass:144.91300

Promethium is the only lanthanide and one of only two elements among the first 83 that has no stable or long-lived (primordial) isotopes.

Radiosotope data

IsotopeMass/DaHalf-lifeMode of decayNuclear spinNuclear magnetic moment
143Pm142.910928265 dEC to 143Nd5/23.8
144Pm143.912586360 dEC to 144Nd51.7
145Pm144.912743 (4)17.7 yEC to 145Nd; α to 141Pr5/2
146Pm145.9146935.53 yEC to 146Nd; β to 146Sm3
147Pm146.9151342.6234 yβ to 147Sm7/22.6
148Pm147.917475.37 dβ to 148Sm12.0
149Pm148.9183302.212 dβ to 149Sm7/23.3
150Pm149.920982.68 hβ to 150Sm1
151Pm150.921201.183 dβ to 151Sm5/21.8

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