Periodic Table/Promethium
← NdSm →
61Pm144.9128 Da

Promethium

Lanthanide·Period 6·f-block

Soft silvery metallic element, belongs to the lanthanoids. Pm-147, the only natural isotope, is radioactive and has a half-life of 252 years. Eighteen radioisotopes have been produced, but all have very short half-lives. Found only in nuclear decay waste. Pm-147 is of interest as a beta-decay source, however Pm-146 and Pm-148 have to be removed from it first, as they generate gamma radiation. Discovered by J.A. Marinsky, L.E. Glendenin and C.D. Coryell in 1947.

Gallery

Photomontage of what promethium metal might look like (it is too radioactive and real images are not available)

Unknown authorUnknown author, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/promethium.php

Bohr model of Promethium

Physical Propertiesmass · density · phase · crystal

Atomic Mass

144.9128Da

Density

7.2600g/cm³

Phase (STP)

Solid

Melting Point

1315.2K

Boiling Point

—

Molar Heat

—

Crystal Structure

—

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

185.00pm

Covalent

173.00pm

Van der Waals

238.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Xe] 4f5 6s2

Electron Shells

2, 8, 18, 23, 8, 2

Electronegativity

—

Electron Affinity

—

1st Ionization Energy

5.6kJ/mol

Oxidation States

+3

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

↑↓
1s2
↑↓
2s2
↑↓
↑↓
↑↓
2p6
↑↓
3s2
↑↓
↑↓
↑↓
3p6
↑↓
↑↓
↑↓
↑↓
↑↓
3d10
↑↓
4s2
↑↓
↑↓
↑↓
4p6
↑↓
↑↓
↑↓
↑↓
↑↓
4d10
↑↓
5s2
↑↓
↑↓
↑↓
5p6
↑
↑
↑
↑
↑
4f5
↑↓
6s2

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f5 6s2Short: [Xe] 4f5 6s2

Ionization Energies (61 known)

1st5.6 kJ/mol2nd10.9 kJ/mol3rd22.4 kJ/mol4th41.2 kJ/mol5th61.7 kJ/mol6th85.0 kJ/mol7th101.0 kJ/mol8th116.0 kJ/mol9th138.0 kJ/mol10th155.0 kJ/mol11th174.0 kJ/mol12th202.0 kJ/mol13th229.0 kJ/mol14th248.0 kJ/mol15th269.0 kJ/mol16th430.0 kJ/mol17th462.0 kJ/mol18th497.0 kJ/mol19th534.0 kJ/mol20th569.0 kJ/mol21th609.0 kJ/mol22th651.0 kJ/mol23th689.0 kJ/mol24th730.0 kJ/mol25th767.0 kJ/mol26th916.0 kJ/mol27th956.0 kJ/mol28th998.0 kJ/mol29th1040.0 kJ/mol30th1113.0 kJ/mol31th1158.0 kJ/mol32th1261.0 kJ/mol33th1308.7 kJ/mol34th2251.0 kJ/mol35th2344.0 kJ/mol36th2443.0 kJ/mol37th2549.0 kJ/mol38th2652.0 kJ/mol39th2755.0 kJ/mol40th2892.0 kJ/mol41th2997.0 kJ/mol42th3112.0 kJ/mol43th3219.0 kJ/mol44th3519.0 kJ/mol45th3613.0 kJ/mol46th3718.0 kJ/mol47th3816.0 kJ/mol48th4056.0 kJ/mol49th4166.0 kJ/mol50th4371.0 kJ/mol51th4476.0 kJ/mol52th10115.0 kJ/mol53th10378.0 kJ/mol54th10671.0 kJ/mol55th10942.0 kJ/mol56th11819.0 kJ/mol57th12136.0 kJ/mol58th12532.0 kJ/mol59th12797.3 kJ/mol60th52144.3 kJ/mol61th53346.3 kJ/molSuccessive Ionization Energies

Emission Spectrumvisible range · characteristic spectral lines

455
470
Pm emission
380nm750nm
455.0 nm(100%)470.0 nm(50%)

Abundanceby mass

Biological Role

No biological role

Radioactive; no biological role.

Discovery

Discovered By

J.A. Marinsky, L.E. Glendenin, C.D. Coryell

Named By

—

Year

1945

Nuclear Data

Known Isotopes

40

Stable Isotopes

0

Stable Mass Numbers

None

Isotopes of Pm40 known

NuclideZNMass (AMU)Half-lifeDecayJπAbundance
126Pm6165125.957327Unknownβ⁺, β⁺p——
127Pm6166126.951358Unknownβ⁺, p3/2+—
128Pm6167127.9482341.00 sβ⁺ (1%), β⁺p, p (0%)4+—
163Pm61102162.953881255 msβ⁻ (1%), β⁻n5/2-—
164Pm61103163.958819Unknownβ⁻, β⁻n5-—
165Pm61104164.962780Unknownβ⁻, β⁻n5/2-—

Click any isotope for its full page with decay chain:

126Pm127Pm128Pm129Pm130Pm131Pm132Pm133Pm134Pm135Pm136Pm137Pm138Pm139Pm140Pm141Pm142Pm143Pm144Pm145Pm146Pm147Pm148Pm149Pm150Pm151Pm152Pm153Pm154Pm155Pm156Pm157Pm158Pm159Pm160Pm161Pm162Pm163Pm164Pm165Pm
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