二氧化碳
èr yǎng huà tàn · HSK 7
carbon dioxide CO2
🫧 two + oxygen + change + carbon = the gas we all breathe out
二 (two) 氧 (oxygen) 化 (transform) 碳 (carbon). Literally: two-oxygen-ified carbon. The formula CO2 is baked right into the name — carbon with two oxygens attached.
二 — two horizontal strokes 一 + 一
二 is an indicative character showing the number two with two simple horizontal lines, parallel to 一 (one) and 三 (three). The form has been stable since oracle bone script. It directly represents the concept of 'two' rather than depicting any physical object.
氧 — gas radical 气 + sheep 羊 (phonetic)
氧 is a modern semantic-phonetic compound coined in the 19th century to name the element oxygen. The 气 radical signals 'gas/vapor,' while 羊 (yáng) supplies the sound. It is not an ancient pictograph but part of a systematic set of element names like 氢 (hydrogen) and 氮 (nitrogen).
化 — person 亻 + spoon/upside-down person 匕
化 is an associative compound showing a standing person 亻 next to 匕, originally a depiction of a person turned upside-down. Together they suggest a figure transforming from one state to another, giving the core meaning 'change' or 'transform'. The character later extended to senses like 'convert', 'influence', and the noun suffix '-ization'.
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.