Astatine is a radioactive chemical element that has the symbol At. The astatine atomic number is 85. It is amongst the rarest naturally occurring element from the crust of the Earth and occurs only when there is a decay of several heavier elements. Its chemical properties are known to be much similar to that of iodine. It has not been much researched because all its isotopes have shorter half-lives. All the information that is known about the At element has been an estimation from knowing its position in the periodic table which is below iodine and by thoroughly studying its chemistry in the extremely diluted solutions. In this article, we will learn about the astatine lament, astatine uses, properties of astatine, its definition, formula, and structure in detail.

What is Astatine?

As per the astatine definition, it is the 85th element in the periodic table that has a symbol At.

It is a type of a radioactive element and is known to be the heaviest among all the other halogens. This element exhibits quite similar chemical properties when compared to the element iodine. The isotopes of astatine have a short half-life of about 8.1 hours, and some isotopes are known to be unstable. It has around seven isotopes in total. This element is a black solid and has a metallic look.

It is considered to be amongst the rarest occurring natural elements. Around 2.36 × 1025grams of the earth’s crust contains astatine that measures around less than 1 gram. Astatine is mainly formed through the decay of the elements thorium and uranium.

Astatine Structure

The astatine structure according to the At chemistry is shown as follows:

Let us now look at some of the physical and chemical properties of astatine.

Properties of Astatine

Symbol of astatine


Atomic number of astatine


Atomic mass


Group of astatine


Period of astatine


Block of astatine


State at 20°C


Astatine electron configuration

[Xe] 4f145d106s26p5

Melting point of astatine

300°C or 572°F or 573 K

Astatine boiling point

350°C or 662°F or 623 K



Relative atomic mass


Key isotopes

210At and 211At

Astatine Uses

Let us now look at the Uses of Astatine.

  1. Since astatine behaves much similar to iodine, it gets secreted in the human thyroid gland. Therefore, it is used in the treatment of diseases related to the thyroid.

  2. The isotope of astatine called as Astatine-211 is used in the procedure of radiotherapy. It is also utilized for the treatment of cancer since it is said to destroy the cancer-causing cells.

Astatine Health Effects

The total amount of astatine that is present in the earth's crust at any given particular time is less than 30 grams. Hence, only a few micrograms of the element have ever been artificially produced. This, along with the element’s short lifetime, gives no reason to consider the effects of astatine on human health.

Astatine is also studied in a few nuclear research laboratories in which the high radioactivity of the element requires a special kind of handling techniques and precautions to be taken.

Astatine is a halogen and it is quite possible that it accumulates in the human thyroid just like iodine. If seen from a chemical point of view, one can easily speculate that toxicity of astatine would be much similar to that of iodine.

FAQ (Frequently Asked Questions)

1. Where is astatine found?

Astatine is one of the rarest occurring natural elements. It is generally found in the crust of the earth. Approximately 2.36 × 1025grams of the crust of Earth consists of astatine. It is mainly formed by the decaying of the thorium and uranium elements.

2. What is the astatine formula?

The astatine formula is given by the symbol of astatine which is At. the atomic number of astatine is 85. The astatine electronic configuration is given by [Xe] 4f145d106s26p5.