Actinium - Ac

Atomic Number 89     Mass Number of Most Important Isotope (227)      State solid    

Color silvery white    Electronegativity 1.3    Melting Point 1050°C    

Boiling Point 3200 ±300 °C      No Natural Isotopes    

Abbreviated Electron Configuration [Rn] 6d¹ 7s²    

Discovered by Andre Debierne in 1899.