Make your own free website on


Information valid for Pm-145 unless otherwise noted

Basic Information

Symbol: Pm
Atomic Number: 61
Mass: (145.0)
Melting Point: Unknown
Boiling Point: Unknown
Number of Protons/Electrons: 61
Number of Neutrons: 84
Classification: Rare Earth
Crystal Structure: Hexagonal
Density @ 293 K: 6.475 g/cm3
Color: Unknown

Atomic Structure

[Bohr Model of Promethium]
Number of Energy Levels: 6

  1. First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 18
    Fourth Energy Level: 23
    Fifth Energy Level: 8
    Sixth Energy Level: 2


Isotope Half Life
Pm-143 265.0 years
Pm-144 360.0 years
Pm-145 17.7 years
Pm-146 5.53 years
Pm-147 2.62 years
Pm-148 5.37 days
Pm-148m 41.3 days
Pm-149 2.21 days
Pm-151 1.18 days


Date of Discovery: 1945
Discoverer: J.A. Marinsky
Name Origin: From the god Prometheus (who stole fire of the sky and gave it to man)
Uses: No uses known
Obtained From: fission products of uranium, thorium, plutonium