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.
The 气 radical over a phonetic taken from 輕/轻 qīng 'light' — literally 'the light gas'.
Where you actually meet it
氢气 (qīngqì) hydrogen gas
The element itself
Hydrogen is the most abundant element in the universe and yet there is essentially no free hydrogen gas on Earth: a molecule that light, in a warm upper atmosphere, drifts away into space. Everything we have is locked into water and into hydrocarbons, and has to be prised out with energy. Liquid hydrogen boils at about twenty degrees above absolute zero, cold enough to freeze solid anything it touches except helium — which is why it is a superb rocket fuel and a miserable thing to store.
Where it sits among the 118
First isolated in 1766.
In living things
Hydrogen is only about a tenth of a body by mass but nearly two thirds of its atoms, most of them locked into water. Its more interesting job is as a bare proton: mitochondria burn food to push protons across an inner membrane, and the protons crowding to get back through turn ATP synthase, a genuine rotary motor with a spinning shaft, which is how almost every cell on Earth pays for everything it does. Free protons are a different order of thing from the hydrogen bound up in water — at neutrality about one ten-millionth of a mole per litre against water's fifty-odd — and that scarcity is what makes pH so sharp a lever: enzymes are shaped closely enough around their active sites that a shift of one unit can stop them working.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
氢Hydrogen in the dictionary →Others built the same way
Every one of these carries 气, and every one is a gas.