Chemisty

atom 係指構成物質的最細單位, 注意! 佢總體係唔帶charge / 電荷的, 例如, C, N, Si, Na 就係atom. atom 肯定係一粒一粒, 唔會"痴"埋.
molecule 係話atom 用covalent bond / 共價鍵連埋的東西, 同樣, 總體唔帶charge; 另外, molecule 可以係monoatomic (單原子), diatomic (雙原子), triatomic (三原子), ..., polyatomic (多原子). 比如, Ar, Ne 係monoatomic; N2, Cl2 係diatomic; O3, SCl2 係triatomic; ...; polythene 聚乙烯係polyatomic; 仲有P4, S8, C60 之類複雜的東西, 這裡不多說, 只是原子用唔同形式"痴"埋一齊... 有興趣則自行查找. 還有的是, atom 可以係molecule, 但係要考慮響室溫室壓下的情況... 例如, He atom平時都係一粒過, 咁佢就同時係atom 同 molecule; 單一粒K 可以響特殊情況出現, 果時係atom, 但就唔係molecule.
順便... 所有noble gas 都係 (monoatomic) molecule.
單一粒molecule / atom 冇辦法用肉眼睇到, 太細了... 但你唔係見到平時個樣咩? 氦氣無色, 碘蒸氣紫色, 白磷白色固體...

Atom means the elements exist on their own. Molecules means that at least two atoms joined together such that they can naturally exist and stable.
noble gas 係atom。
所以molecule係兩粒或以下的原子痴埋!
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