85
Room of the Elements · No. 85
Astatine (At): what kind of element is it?
日本語
In short
Astatine is element number 85, with the symbol At. Its name comes from astatos, the Greek word for “unstable.”
Atomic number 85(210)
AtAstatineアスタチン (asutachin)- Symbol
- At
- Atomic weight
- (210)
- Place in the table
- Period 6 · Group 17
The number in parentheses is not an atomic weight. It is the mass number of one radioactive isotope of the element.
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
An “unstable” artificial element
Astatine was discovered in 1940 and is an artificial element. It was given a name meaning “unstable.”
Where it sits on the table
Astatine is in the sixth row of Group 17. From the top: fluorine, chlorine, bromine, iodine, astatine.
Think about it
- Q1Do you think “unstable” describes it well?
- Q2Look for elements made by people in the Room of the Elements.
- Q3Do you think astatine, at the bottom of Group 17, is like the others above it?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Names of elements made by people include technetium (“artificial,” 1937) and astatine (“unstable,” 1940).