Astatine Element: Structure, Uses & Properties

Instructor: Tawnya Eash

Tawnya has a master's degree in early childhood education and teaches all subjects at an elementary school.

Astatine is one of the rarest elements on Earth; it decays, or breaks down, so quickly you can never really see it. In this lesson, you'll learn more about the element astatine and its uses and properties.

What is Astatine?

What do these nickels have to do with astatine?

Five nickels weigh 25 grams.
Astatine in nature

It turns out that astatine, a halogen and nonmetal element with the atomic number 85, is one of the rarest elements found on Earth. The amount of naturally present astatine, about 25 grams at any given moment in time, is equal to the weight of five nickels. Try holding five nickels in your hand - you'll see they don't weigh much!

Elements are substances that cannot be broken down into smaller substances. There are up to 120 different elements found on Earth and each one has unique properties. However, some elements have similar properties.

Astatine is one of five different types of halogens or nonmetals, very reactive, toxic elements that when combined with metals can be used to create acids and salts. The other four halogen elements include:

  • Fluorine: found in toothpaste and water to keep teeth strong
  • Chlorine: used to kill bacteria in pools and other water sources
  • Bromine: combined with other elements for use in fire extinguishers
  • Iodine: added in small amounts to table salt

The most common types of astatine are: Astatine-210 and Astatine-211.

Let's learn more about where this rare element is found.

Where Do We Find Astatine?

At the beginning of the 20th century, astatine was actually created, not found. In 1940, a group of scientists - Dale R. Coson, Kenneth Ross Mackenzie and Emilio Segrè - discovered a way to create Astatine-211 using other elements and technology in a lab. In 1943, Berta Karlik and Traude Bernert found astatine in the Earth's crust. This tiny amount of astatine is found after the elements uranium and thorium decay or break down.

Astatine is very rare, and any that's created does not have a long life. Astatine-210 begins to decay to half of its original size in only eight hours - about as long as a school day.

How Do Scientists Describe Astatine?

We describe elements by breaking them down into their most basic part: an atom. All atoms have protons and neutrons in their nucleus or center. The nucleus is surrounded by shells of electrons. The outermost shell of electrons reacts with other elements.

The atomic number for astatine is 85, which means that there are 85 protons in the nucleus. The most commonly created type of astatine has 125 neutrons, with 85 electrons spread among six different shells.

The symbol for astatine on the Periodic Table of Elements is 'At.' Take a look at the symbol and atom of astatine.

Astatine: symbol and atomic structure
Symbol At

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