Atomic number: 89

Symbol: Ac

Category: actinide (transition metal)

Density at 25°C: solid: density: 10 g·cm−3

Welcome to the actinoids or actinides, the last row (series) of elements on the periodic table. Actinium is the first element in this series. Being this far down the periodic table means it is unstable and radioactive.

Use, natural applications or common combinations: 

  • very rare
  • found in uranium ores
  • 225Ac is applied in some medicine for radiation therapy

Basic characteristics:

  • Standard atomic weight: (227)
  • Melting point: 1050 °C
  • Boiling point:  3198 °C
  • Radioactivity: all radioactive
  • 227Ac is naturally occurring with a half-life of 21.772 years is the most stable. decays via alpha and beta.