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61 · Pm

Promethium

The announcements of the 1920s are not upheld. Identified at Oak Ridge in 1945.

Identity

Atomic number
61
Symbol
Pm
Canonical name
Promethium
Category
lanthanide
Group
unassigned
Period
6
Block
f
Former names
illinium, florentium

Series set apart from the main table. Whether group 3 is lanthanum or lutetium (actinium or lawrencium) is still discussed, so the group is left empty.

Properties

These quantities come from the Periodic Table JSON compilation. They have not yet been checked, one by one, against CIAAW atomic weights or NIST measurements. A value marked estimated is not a measurement.

Atomic mass
[145] No standard atomic weight. The number shown is the conventional mass number used in tables, not a measured mass in u.
Electron configuration
[Xe] 4f5 6s2
Electrons per shell
2, 8, 18, 23, 8, 2
Standard state
solid
Density
7.26 g/cm³
Melting point
1,315 K
Boiling point
3,273 K
Electronegativity
1.13 Pauling
First ionization energy
540 kJ/mol
Electron affinity
12.45 kJ/mol

Notable isotopes

This summary is not an inventory of every isotope.

Conventional mass number: 145

History

Illinium and florentium

Discovery · rejected · 1926

Several announcements of the 1920s, under the names illinium and florentium, are not upheld as the discovery of element 61.

Promethium at Oak Ridge

Discovery · confirmed · 1945

Marinsky, Glendenin, and Coryell identify element 61 in fission products. The public announcement follows in 1947.

See the element timeline

Etymology

Theme
mythology
Language
grec
Root
Prometheus
Meaning
Prometheus

Scientists

Places and institutions

  • Oak Ridge — historical setting : United States — present country : United States

Sources