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
氧气 (yǎngqì) oxygen
The element itself
By mass, oxygen is the most abundant element in Earth's crust — close to half of it — because the rock-forming silicate minerals are essentially frameworks of oxygen atoms with metals tucked into the gaps. Stand on a granite outcrop and you are standing mostly on oxygen. The atmospheric kind is the odd part: free O₂ is chemically aggressive and would vanish within a few million years without life continually replenishing it, so a planet with an oxygen atmosphere is a planet with something on it doing the work.
Where it sits among the 118
First isolated in 1774.
In living things
Oxygen makes up about 65% of a human by mass, mostly as water, but the reason we breathe is a single point at the end of the respiratory chain, where cytochrome c oxidase hands four electrons and four protons to one O₂ molecule and turns it into water. That reaction releases far more energy than any fermentation, which is why animals of any size only became possible once the air had oxygen in it. The bargain is that the same reactivity attacks the cell from inside: partly reduced oxygen leaks out as superoxide, and every aerobic organism carries dedicated enzymes — superoxide dismutase, catalase — whose entire job is cleaning up after the gas that keeps it alive.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
氧Oxygen in the dictionary →Others built the same way
Every one of these carries 气, and every one is a gas.