astatine

American  

[as-tuh-teen, -tin] / ˈæs təˌtin, -tɪn /

noun

Chemistry.

1. a rare element of the halogen family. At; 85.

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astatine British  

/ -tɪn, ˈæstəˌtiːn /

noun

1. a radioactive element of the halogen series: a decay product of uranium and thorium that occurs naturally in minute amounts and is artificially produced by bombarding bismuth with alpha particles. Symbol: At; atomic no: 85; half-life of most stable isotope, ²¹⁰ At: 8.1 hours; probable valency: 1,3,5, or 7; melting pt: 302°C; boiling pt: 337°C (est)

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astatine Scientific  

/ ăs′tə-tēn′ /

1. A highly unstable, rare, radioactive element that is the heaviest of the halogen elements. Its most stable isotope has a half-life of 8.3 hours. Atomic number 85; melting point 302°C; boiling point 337°C; valence probably 1, 3, 5, 7.

2. See Periodic Table

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Etymology

Origin of astatine

1945–50; < Greek ástat ( os ) not steadfast, unstable ( see astatic) + -ine ²

Example Sentences

When astatine decays, it emits alpha particles -- tiny clusters made of two protons and two neutrons -- that can release powerful, localized bursts of energy.

From Science Daily • Nov. 11, 2025

"We are one of a handful of U.S. centers capable of routinely producing astatine in medically relevant quantities and delivering it to nearby facilities."

From Science Daily • Nov. 11, 2025

There are no stable isotopes of astatine; all decay with half-lives in the order of hours at the most, seconds to minutes for the most part.

From Nature • Sep. 1, 2020

These are the elements fluorine, chlorine, bromine, iodine, and astatine.

From Textbooks • Feb. 14, 2019

Astatine was first made at Berkeley by bombarding bismuth with alpha particles, which produced astatine and released two neutrons.

From A Brief History of Element Discovery, Synthesis, and Analysis by Watson, Glen W.