What is Actinium

A radioactive metal, actinium (pronounced as ak-TIN-ee-em) belongs to the family of actinide metals and denoted by the chemical symbol Ac ^[1].

Actinium Isotopes

It has 29 isotopes out of which actinium-227 is the most stable one, having a half-life of 21.17 years. After which, it either undergoes alpha decay into francium-223, or beta decay into thorium-227 ^[3].

Where is Actinium Found

The element occurs in uranium ore deposits formed as a result of radioactive decay of uranium and its other radioisotopes. Its abundance in earth’s crust is estimated to be 0.0005 parts per trillion by mass ^[4].

History

Origin of its Name: It derives its name from the Greek word, ‘aktis’, meaning a ‘beam’ or ‘ray’.

Who Discovered Actinium: Andre Debierne, a French Chemist, discovered the element.

When and How was it Discovered

In 1899, Debierne at Paris while finding out new methods to separate rare earth oxides extracted the element from uranium-rich pitchblende ores. In 1902, Friedrich Otto Giesel who was unaware of Debierne’s discovery independently worked on the same mineral ore to extract the element and even named it emanium. However, the original name ‘actinium’ was decided to be retained ^{[1, 2]}.

Classification and Position of the Element on the Periodic Table ^[1]

Group	Unknown
Period	7
Block	d

Properties of Actinium ^{[1, 2, 3]}

General Properties
Relative atomic mass	227
Atomic mass	227 atomic mass units
Physical Properties
Color/appearance	Silver white
Luster	Unknown
Odor	Unknown
Malleability	Unknown
Ductility	Unknown
Melting point/freezing point	1050 °C (1922 °F)
Boiling point	3200 °C (5792 °F)
Density	10 g/cm3
State of matter at room temperature  (solid/liquid/gas)	Solid
Hardness	Unknown
Chemical Properties
Flammability		Unknown
Oxidation state/Oxidation number		(+2), +3

Atomic Data of Actinium ^{[1, 2, 3]}

Common Uses of Actinium

Although a good source of alpha rays, it has no specific commercial applications, except in laboratory research ^[2].

Due to actinium’s high activity levels, it might be effective in generating neutrons. While some research studies show the effectiveness of actinium-225 in the treatment of prostate cancer ^[5], actinium-227 might be useful in thermoelectric generators of spacecraft ^[4].

Actinium Health Hazards

Accidental ingestion of Ac leads to deposition in the bones and liver, causing severe damage like cancer due to radioactive decay ^[4].

Interesting Facts

• Debierne may have worked with Marie Curie during the actinium’s discovery as the pitchblende sample used by him was the one from which radium and polonium had already been extracted by the latter ^[4].
• Actinium glows blue in the dark as a result of ionization of gases in the air caused by its radioactivity ^[4].
• It is about 150 times heavier than radium ^[4].

What is the Cost of Actinium

Since production of the metal on a commercial scale is expensive, it cannot be availed outside of laboratory production.

References

1. http://www.rsc.org/periodic-table/element/89/actinium
2. https://education.jlab.org/itselemental/ele089.html
3. https://www.chemicool.com/elements/actinium.html
4. https://www.thoughtco.com/interesting-facts-about-actinium-603672
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5565267/