How the character is built
The 气 radical marks this as a gas, and that is not a coincidence of this one character — it holds right across the table. Read the radical first and the element's state at room temperature is already settled.
Where you actually meet it
含氟牙膏 (hánfú yágāo) fluoride toothpaste
The element itself
Fluorine is the most reactive element in the table, and prising it loose defeated chemists for most of a century — several were badly poisoned trying before Henri Moissan finally isolated it by electrolysis at very low temperature. Nearly all of it comes from fluorite, the mineral that gave fluorescence its name after it was noticed glowing under certain light. Fluorite earned its own name earlier still, from the Latin for flow: added to a furnace it makes slag run thin, and steelmakers were using it as a flux long before anyone knew there was an element in it.
Where it sits among the 118
First isolated in 1886.
In living things
Fluoride has no known essential role in the body, but it has an unmistakable affinity for teeth. Enamel is a crystal of hydroxyapatite, and fluoride will swap in for the hydroxide, giving fluorapatite, which dissolves at a lower pH — though the modern picture is less about what gets built into a tooth during childhood than about fluoride sitting in saliva and plaque, tipping the endless dissolve-and-rebuild at the enamel surface back towards rebuild. It also shows what happens when a geological accident supplies too much: in regions where groundwater runs naturally high in fluoride, teeth develop with a permanent mottling in the enamel.
Where it comes from in China
Fluorite, the ore of fluorine and a mineral pretty enough to be carved, is abundant in Zhejiang, where shallow volcanic and granitic rocks are cut by veins of it, and again in Inner Mongolia and Jiangxi. Fluorine is one of those elements that stays dissolved in a magma's last watery fluids and travels a long way before precipitating, which is why fluorite veins tend to sit around and above granites rather than inside them. It is the raw material behind refrigerants, aluminium smelting and the fluoropolymers, so it matters more than its low profile suggests.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
氟Fluorine in the dictionary →Others built the same way
Every one of these carries 气, and every one is a gas.