Actinium

Actinium is a radioactive metal with the symbol Ac and atomic number 89. It was discovered in 1902 by Friedrich Oskar Giesel. It is the first element in the actinide series on the periodic table. It is found in uranium ores and is highly radioactive. Actinium’s most common use is in the production of neutrons for research.

In this article, we will learn about the element Actinium in detail, including its discovery, properties, uses, and effects.

Actinium Element Information

Here is some basic information on the element Actinium of the periodic table.

Property	Description
Symbol	Ac
Category	Actinide
Period	7
Block	f-block
Atomic Number	89
Atomic Mass	227 atomic mass units (amu)
State at 20°C	Solid
Electron Configuration	[Rn] 6d1 7s2
Common Isotopes	Actinium-227

What is Actinium?

Actinium is a rare and highly radioactive element. It is denoted by the symbol Ac and has an atomic number of 89.

Actinium is the first element of the actinide series in the periodic table. It occurs naturally in uranium and thorium ores. It is more than 150 times less abundant than uranium. Actinium glows pale blue in the dark due to its intense radioactivity.

Actinium Discovery

Actinium was discovered in 1899 by the German chemist Friedrich Oskar Giesel. He initially isolated it as a substance that emitted intense radiation, which glowed in the dark. Giesel named it “Actinium”. It came from the Greek word “aktinos,” meaning ray, reflecting its strong radiative powers.

In 1902, the famous French chemist André-Louis Debierne independently discovered actinium. He described it as a substance similar to titanium and (incorrectly) thorium. Later analysis confirmed that both Giesel and Debierne had discovered the same element.

Actinium Symbol

The symbol of actinium element is shown below:

Properties of Actinium

Properties of Actinium can be studied in following two categories

• Physical Properties of Actinium
• Chemical Properties of Actinium

Let’s learn them in detail

Physical Properties of Actinium

These are some of the physical properties of Actinium:

Property	Description
State at 20°C	Solid
Color/Appearance	Silvery-white, glowing pale blue in the dark
Melting Point	1050°C
Boiling Point	3200°C
Density	Approximately 10 g/cm³ at room temperature
Radioactivity	Highly radioactive
Malleability	High
Ductility	Low
Conductivity	Good electrical conductor
Crystal Structure	Face-centered cubic (fcc)
Magnetic Properties	Paramagnetic

Chemical Properties of Actinium

Actinium is highly reactive as it comes from the actinide series. Its electropositive nature and radioactive decay properties influence its various reactions.

Reactivity with Oxygen

• Actinium reacts with oxygen quickly when exposed to air.
• It forms Actinium(III) oxide, represented by the formula Ac₂O₃​.
• Actinium tarnishes in air due to oxidation. It forms a white oxide coating that protects deeper layers from further oxidation.

4Ac + 3O₂ ​→ 2Ac₂​O₃​

Reaction with Water

• Actinium does not react noticeably with cold water.
• It reacts with steam, forming Actinium(III) hydroxide.
• The reaction can be written as:

2Ac + 6H₂O → 2Ac(OH)₃ + 3H₂

Reactivity with Acids

• Actinium dissolves in acids.
• Actinium dissolves easily in acids such as hydrochloric acid and sulfuric acid. When Actinium reacts with hydrochloric acid, it forms actinium(III) chloride, releasing hydrogen gas in the process. The chemical equation is given by :

Ac + 6HCl → 2AcCl₃ + 3H₂

• Actinium also reacts with sulfuric acid to produce actinium(III) sulfate and hydrogen gas. The equation for this reaction is:

2Ac + 3H₂SO₄ → Ac₂(SO₄)₃ + 3H₂

Reaction with Halogens

Actinium reacts with halogens, forming halides.

• It reacts vigorously with fluorine to form Actinium(III) fluoride. The chemical reaction is as follows: 2

 Ac +3F₂ → 2AcF₃

In this reaction, Actinium fluoride (AcF₃​) is produced as a white solid.

• Actinium also reacts with chlorine gas to produce Actinium(III) chloride. The equation for this reaction is:

2Ac + 3Cl₂ → 2AcCl₃

Actinium chloride (AcCl₃​) forms as a white solid.

Uses of Actinium

Here are some of the most common uses of Actinium

• Actinium-225 is used in medicine for targeted alpha therapy (TAT).
• This isotope is effective in treating cancers, such as leukemia and lymphoma.
• It targets cancer cells without harming the surrounding healthy tissue.
• Actinium is also used in neutron emitters for research in neutron radiography.
• Researchers utilize it to study the structure of materials due to its neutron emission.
• Actinium’s isotopes are used7 in the production of neutrons in research reactors.

Effects of Actinium

Actinium is highly radioactive, which makes handling it extremely hazardous. Exposure to it has many health and environmental risks.

Environmental Effects of Actinium

• Actinium’s radioactivity can contaminate soil and water bodies.
• It poses risks to wildlife, potentially causing mutations or death.
• Contaminated environments may remain unsafe for long periods due to Actinium’s long half-life.
• Handling and disposal require strict regulations to prevent accidental releases.
• Plants and microorganisms may absorb Actinium, entering the food chain.
• Cleanup of Actinium contamination is complex and costly, requiring specialized techniques.

Health Effects of Actinium

• Exposure to Actinium can cause acute radiation sickness.
• Symptoms include nausea, vomiting, fatigue, and loss of hair.
• Long-term exposure significantly raises the risk of cancer.
• Actinium emits gamma rays and neutrons, which penetrate tissues deeply.
• Protective measures are crucial for those handling Actinium to avoid exposure.
• Proper storage and minimal handling reduce risks of accidental poisoning.

FAQs on Actinium

What is Actinium?

Actinium is a rare, silvery-white, highly radioactive metal with the atomic number 89. It was discovered in 1902 and is the first element in the actinide series.

Where is Actinium found?

Actinium is found in trace amounts in uranium and thorium ores, from which it is isolated.

What is the use of Actinium?

Actinium is primarily used in medicine for targeted alpha therapy to treat cancers, and as a neutron source for scientific research.

What are the key properties of Actinium?

Actinium is radioactive, reacts quickly with oxygen, and has a high melting point. It emits strong gamma rays and neutrons.

Is Actinium naturally occurring?

Actinium is both naturally occurring and synthetic. Natural actinium is derived from uranium ores, while synthetic versions are produced in nuclear reactors.

How is Actinium stored and handled?

Actinium is stored in shielded containers, and handling requires strict protocols, specialized equipment, and protective clothing to minimize radiation exposure.