Symbol Ac
Atomic Number 89
Atomic Mass 227 g mol -1
Discovered by Andre Debierne in 1899

Chemical Properties of Actinium

Group Actinides Melting point 1050°C, 1922°F, 1323 K
Period 7 Boiling point 3200°C, 5792°F, 3473 K
Block d Density (g cm−3) Unknown
Atomic number 89 Relative atomic mass [227]
State at 20°C Solid Key isotopes 227Ac
Electron configuration [Rn]  6d17s2 CAS number 7440-34-8
ChemSpider ID 22404 ChemSpider is a free chemical structure database

What is Actinium?

Actinium is the first element of the actinide series. All 36 known isotopes of actinium are radioactive. Ac 227 and 228 are naturally occurring isotopes with the half-life of 21.77 years and 6.13 hours respectively. It is 150 times more radioactive than radium. It is hazardous to health. If ingested, it gets deposited into the liver and bones, damaging the cells due to radioactive decay.

  • Actinium is a radioactive element with an atomic number 89 of the periodic table.
  • It has the physical appearance of metallic silver.
  • In nature, it is found in traces of most of the Uranium ores.
  • Due to intense radioactivity, this metal glows blue in the dark.
  • It also shares similar properties to that of lanthanum.

Uses of Actinium

It is found naturally in uranium ores. It rarely occurs as a free element in the earth’s crust. It is more frequently produced in the lab.

  • It is a vital source of alpha rays.
  • Ac 225 is used in the field of medicine as an agent for radiation therapy.
  • It has immense value as a neutron source as it is one fifty times more radioactive than compared to radium.
  • Ac does not find much significant use in any industrial application.

Properties of Actinium

  • This radioactive element reacts with oxygen to form a white coating like substance called actinium oxide. Thus preventing the metal from further getting oxidized.
  • The actinium ions appear colorless when kept in a solution. It is one of the strongest of radioactive elements.

Practise This Question

Which of the following pairs of d-orbitals will have electron density along the axis?