Periodic table / Actinium

Overview

Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902.

Electron configuration

The electron configuration of Actinium is [Rn] 6d1 7s2, with electron shells of 2, 8, 18, 32, 18, 9, 2.

Physical and chemical properties

Actinium is classified as a actinide. It has an atomic mass of 227 and exists as a solid at standard conditions.

Real-world uses of Actinium

Actinium is an actinide studied primarily in nuclear science and research due to its radioactive properties.

Interesting facts about Actinium

• Actinium has the atomic number 89 and chemical symbol Ac.
• It belongs to period 7, group 3 of the periodic table.
• Actinium was discovered by Friedrich Oskar Giesel.

Explore Actinium interactively

Want to compare Actinium with other elements or see it highlighted on the full table? Open the interactive periodic table and click on Ac to explore properties, trends, and neighboring elements. You can also test your knowledge with our periodic table quiz game.