分子(molecule)
纯物质可以分割而保持其组成和化学特性不变的最小可辨认单位。再分成更小的部分，最终为原子，那就要破坏将分子结合在一起的化学键。对於稀有气体来说，分子就是单原子；所有其他的物质的分子中都有两个（双原子）或多个（多原子）原子。元素中的原子都是相同的，比如氢气（H2），而化合物分子中的原子是不同的，比如葡萄糖（C6H12O6）。原子总是按固定的比例结成分子。不同物质的分子可以有相同的组成原子，但可能它们的比例不同，像一氧化碳（CO）和二氧化碳（CO2），或者是以不同的方式结合（参阅isomer）。分子中的共价键给定了分子的形状以及分子的大部分性质。（对於以离子键结合的固体，分子的概念已经不重要了。）用现代技术及电脑进行分析，可以确定并显示出分子的大小、形状以及构型，即各原子核和电子云的位置、化学键的长度和角度以及其他的细节。电子显微技术甚至可以提供个别分子和原子的像。亦请参阅molecular weight。
English version：
molecule
Smallest identifiable unit into which a pure substance can be divided and retain its composition and chemical properties. Division into still smaller parts, eventually atoms, involves destroying the bonding that holds the molecule together. For noble gases, the molecule is a single atom; all other substances have two (diatomic) or more (polyatomic) atoms in a molecule. The atoms are the same in elements, such as hydrogen (H2), and different in compounds, such as glucose (C6H12O6). Atoms always combine into molecules in fixed proportions. Molecules of different substances can have the same constituent atoms, either in different proportions, as in carbon monoxide (CO) and carbon dioxide (CO2), or bonded in different ways (see isomer). The covalent bonds in molecules give them their shapes and most of their properties. (The concept of molecules has no significance in solids with ionic bonds.) Analysis with modern techniques and computers can determine and display the size, shape, and configuration of molecules, the positions of their nuclei and electron clouds, the lengths and angles of their bonds, and other details. Electron microscopy can even produce images of individual molecules and atoms. See also molecular weight.
