碳Carbon

碳有四个价电子，通过 sp³、sp²、sp 杂化形成单键、双键和三键。C–C 键能高（约 346 kJ/mol），而且与 C–H、C–O 键能相近，使碳链化合物既稳定又能多样转化，这种“成链性”是有机化学存在的基础。¹²C 被定义为原子质量单位的基准。

Carbon has four valence electrons and forms single, double and triple bonds through sp³, sp² and sp hybridisation. The C–C bond is strong (about 346 kJ/mol) and close in strength to C–H and C–O bonds, so carbon chains are stable yet versatile; this catenation is the basis of organic chemistry. ¹²C was long the reference for the atomic mass unit.

木炭和炭黑自史前就被使用。1772 年拉瓦锡证明金刚石燃烧只生成二氧化碳，说明它与木炭是同一种元素；1779 年舍勒证明石墨也是碳。拉瓦锡在 1789 年把它列为元素，名称来自拉丁文 carbo（木炭）。中文“碳”字由“炭”加石字旁而来。

Charcoal and soot have been used since prehistory. In 1772 Lavoisier showed that burning diamond gives only carbon dioxide, so it is the same element as charcoal, and in 1779 Scheele showed that graphite is carbon too. Lavoisier listed it as an element in 1789; the name comes from Latin carbo, charcoal. The Chinese character 碳 was formed by adding the stone radical to 炭, charcoal.

金刚石中每个碳 sp³ 杂化形成三维网络，是天然最硬的物质；石墨为 sp² 层状结构，层内导电、层间可滑动；1985 年发现的 C₆₀ 富勒烯、1991 年表征的碳纳米管和 2004 年分离的石墨烯，开辟了碳纳米材料领域。常温常压下石墨是热力学稳定相。

In diamond each carbon is sp³ hybridised in a three-dimensional network, the hardest natural substance; graphite is layered sp² carbon that conducts within layers and slides between them. C₆₀ fullerene (1985), carbon nanotubes (characterised in 1991) and graphene (isolated in 2004) opened the field of carbon nanomaterials. Graphite is the stable phase at ordinary conditions.

碳以煤、石油、天然气形式提供大部分人类能源；焦炭用于冶金还原；活性炭用于吸附；碳纤维用于航空材料。¹⁴C 测年可测定约五万年以内的有机遗存年代。碳循环与大气 CO₂ 浓度直接影响全球气候。

As coal, oil and natural gas, carbon supplies most human energy; coke reduces ores in metallurgy; activated carbon adsorbs impurities; carbon fibre goes into aircraft. Radiocarbon (¹⁴C) dating gives ages for organic remains up to about 50,000 years. The carbon cycle and atmospheric CO₂ directly affect the global climate.