Fluorine is element number 9, with the symbol F. Compounds of fluorine, called fluorides, are used to help prevent tooth decay.
Atomic number 919.00
FFluorineフッ素 (fusso)
Symbol
F
Atomic weight
19.00
Place in the table
Period 2 · Group 17
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
Named for fluorspar and “flow”
The symbol F comes from the English name of the mineral fluorspar, which contains fluorine, and from the Latin word for “flow.”
Fluorine was discovered in 1886, near the end of the 19th century, later than many other elements.
Fluoride against tooth decay
According to a Ministry of Health guide, when fluoride acts on the surface of the teeth again and again, it can strengthen the teeth, help early decay repair itself (remineralization) and more, and is expected to help prevent tooth decay.
Fluorine is in the second row of Group 17. Directly below it is chlorine.
Think about it
Q1Check at home whether your toothpaste contains fluoride.
Q2Why do you think it took so long to discover fluorine?
Q3Fluorine and chlorine share a column. In what ways might they be alike?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Group 17 includes fluorine, chlorine and bromine. Chlorine is named for “yellow-green” and bromine for “stench.”