Pm

Promethium · element 61

Lanthanide · Solid at room temperature

Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.

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

Key facts

Atomic mass
145 u
how heavy one atom is
Phase (room temp.)
Solid
Density
7.26 g/cm³
how tightly packed it is
Melting point
1315 K (1042 °C)
when solid turns to liquid
Boiling point
3273 K (3000 °C)
when liquid turns to gas
Period
6
its row in the periodic table
Group
3
its column in the periodic table
Block
F-block
the neighbourhood it lives in
Electronegativity
1.13
how strongly it pulls electrons
Electron configuration
[Xe] 4f5 6s2
where its electrons live
Shells
2 · 8 · 18 · 23 · 8 · 2
electrons in each layer, inside to out
Discovered by
Chien Shiung Wu
who found it
Named by
Isotopes of promethium
who gave it its name
Appearance
metallic
what it looks like

Source: Wikipedia

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