actinium

Actinium is a chemical element with the symbol Ac and the atomic number 89. It is a radioactive element that is not found naturally on Earth. Actinium is the first member of the actinide series, which is a group of elements that are all radioactive.

Actinium is a silvery-white, radioactive metal that is very reactive. It is a member of the actinide group, which is a group of elements that are very reactive and combine easily with other elements. Actinium is also a radioactive element, which means that it breaks down over time and emits radiation.

Actinium was first discovered in 1899 by Pierre and Marie Curie. The element was named after the Greek word "aktinos," which means "ray."

Actinium is not used for any practical purposes. However, it is a valuable research tool for scientists who study nuclear physics.

Here is a fun fact about actinium:

• Actinium is so radioactive that it has a half-life of only 21.7 years. This means that half of a sample of actinium will decay into other elements in 21.7 years.

Actinium is a silvery-white, radioactive metal that is very reactive.