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.
Gas radical wrapped round 冬 dōng — and unusually the sound is taken from the second syllable of ra-DON.
This character is used for the element and little else — you are unlikely to meet it outside a chemistry classroom.
The element itself
Radon is a noble gas produced by the decay of radium, which in turn comes from uranium, so it is being generated continuously inside any rock with uranium in it — granite especially. Being a gas, it escapes and diffuses, and being heavy, it collects in enclosed spaces below ground level, which is why houses in certain geological districts are tested and ventilated. Its half-life of under four days means it is entirely a product of what is happening underneath, right now.
Where it sits among the 118
First isolated in 1900.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
氡Radon in the dictionary →Others built the same way
Every one of these carries 气, and every one is a gas.