Praseodymium (Pr)

Praseodymium and neodymium spent forty years as a single supposed element called didymium until Welsbach separated them in 1885; the names mean green twin and new twin. Didymium glass has a sharp absorption band that swallows the intense sodium-yellow flare of hot glass, which is why glassblowers wear it — the glass looks colourless through the lens while the flare vanishes. Most magnet production uses the two as an unseparated NdPr alloy, because separating them costs money and the magnets barely notice.

Properties

Atomic number

59

Symbol

Pr

Standard atomic weight

140.91 u

Category

Lanthanide

Period

6

Block

f-block

Electron configuration

[Xe] 6s² 4f³

Electrons per shell

2, 8, 18, 21, 8, 2

Melting point

1,204 K — 930.9 °C — 1707.5 °F

Boiling point

3,793 K — 3519.8 °C — 6367.7 °F

Density

6.77 g/cm³

Electronegativity

1.13 (Pauling)

Oxidation states

+3

Discovered

1885 by Carl Auer von Welsbach

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f³

Noble gas shorthand

[Xe] 6s² 4f³

Shells

K: 2 · L: 8 · M: 18 · N: 21 · O: 8 · P: 2

What it is used for

• Neodymium-praseodymium magnets, where the two are used together
• Welder's and glassblower's goggles, which it tints yellow-green
• Didymium glass for photographic filters
• Fibre-optic signal amplifiers
• Yellow ceramic glazes

Neighbours in the table