How the character is built
The 钅 radical marks this as a metal, 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. It is 金 (jīn) squeezed into the space beside another component — radicals change shape by position, which is why 金 is hard to spot until you know to look for 钅.
This character is used for the element and little else — you are unlikely to meet it outside a chemistry classroom.
The element itself
Rubidium is named for the deep red lines it showed in the spectroscope, the instrument that had just been invented and was busily turning up elements nobody had suspected. It never forms minerals of its own, tagging along instead wherever potassium goes because the two ions are a similar size, so it is recovered as a minor by-product of lithium and caesium mining. One of its isotopes decays extremely slowly to strontium, which gives geologists a clock good for dating rocks billions of years old.
Where it sits among the 118
First isolated in 1861.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
铷Rubidium in the dictionary →Others built the same way
Every one of these carries 钅, and every one is a metal.