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.
Source of the gaming slang 氪金 — but by a detour: the word is Japanese 課金 kakin 'to charge/pay', respelled with the homophone 氪 (from 氪石, a fictional game metal). The element supplied the sound, not the meaning.
Where you actually meet it
氪金 (kèjīn) to spend real money in a game
The element itself
Krypton is about a millionth of the air, skimmed off liquid air as a leftover, which is roughly as interesting as it sounds — except that for twenty-three years krypton was the metre. From 1960 the length was defined as 1,650,763.73 wavelengths of one orange-red line emitted by krypton-86, a definition that retired the scratched platinum bar kept outside Paris and held the job until the speed of light took it over in 1983. For that stretch, every measured distance on Earth was counted out in the light of this gas.
Where it sits among the 118
First isolated in 1898.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
氪Krypton in the dictionary →Others built the same way
Every one of these carries 气, and every one is a gas.