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.
Phonetic 土 tǔ 'earth' — sound only, though the accident is a happy one for an ore metal.
This character is used for the element and little else — you are unlikely to meet it outside a chemistry classroom.
The element itself
Thorium is several times more abundant in the crust than uranium and is effectively a single isotope with a half-life about as long as the age of the universe, which makes it far less alarming than its reputation. It occurs mostly in monazite, a dense phosphate mineral that concentrates in heavy-mineral beach sands — the black sands of Kerala are the classic example. Almost nobody mines it deliberately; it comes up as an unwanted radioactive passenger with rare earths, and the cost of handling it has shaped where rare-earth processing can be done at all.
Where it sits among the 118
First isolated in 1829.
Where it comes from in China
Thorium has no mine of its own in China, or anywhere much — it comes up as a passenger. The thorium ion is close enough in size and charge to the light rare earths to slot straight into monazite and bastnäsite, so every light rare-earth deposit is also a low-grade thorium deposit whether anyone wants one or not. That is why the tailings at Bayan Obo are mildly radioactive, and why rare-earth processing anywhere carries a radioactive-waste problem that has nothing to do with the metals being sold.
The full entry
For stroke order, example sentences, audio and the complete set of meanings, see the dictionary entry.
钍Thorium in the dictionary →Others built the same way
Every one of these carries 钅, and every one is a metal.