Atomic number: 57

Symbol: La

Category: lanthanoid metal

Density at 25°C: solid: density: 6.162 g·cm−3

Welcome to the lanthanoids or lanthanides, the IUPAC prefers lanthanoids to avoid confusion with ions that often have _ides at the end. This is the first element in that part of the periodic table that is usually separate at the bottom. Most lanthanum is used as part of rechargeable batteries particularly nickel metal hydride batteries.

Lanthanum sample in a glass tube. image: adapted from wikipedia

Use, natural applications or common combinations: 

  • batteries
  • for fibre optics to improve transmission of IR light
  • some alloys
  • lighters and flint

Basic characteristics:

  • Standard atomic weight: 138.905 47(7)
  • Melting point:  920 °C
  • Boiling point: 3464 °C
  • Radioactivity: mostly naturally stable,  small amounts of 138La with half life of 1.05×1011 y  via beta -