碳
tàn · HSK 7
carbon (chemistry)
💎 碳 = 石 stone radical + 炭 charcoal (tàn); charcoal is the sound clue too
The 石 radical marks it as a mineral/element, while 炭 (charcoal) supplies both the meaning and the tàn sound. Both charcoal and diamond are pure carbon, which ties the parts together.
碳 — fire radical 火 + 炭 (charcoal)
碳 is a modern semantic-phonetic compound coined for the chemical element carbon. The fire radical 火 signals its connection to burning and combustion, while 炭 ('charcoal') supplies both the sound and the meaning hint, since charcoal is largely carbon. The character entered Chinese in the 19th century as Western chemistry was translated.