The concept of molecular structure is one of the most important concepts of chemistry. In fact, molecular structure is closely related to the concept of chemical substance and its set of properties, and it is the main factor in the explanation of reactivity. In fact, much of the behavior of substances is explained in terms of the structure of their component molecules. This may explain why people tend to take the notion of molecular structure for granted. However, the problem begins already when it comes to specifying the concept, since there is no clear definition of ‘molecular structure’ valid for all chemistry. The purpose of the present article is to show that the term ‘molecular structure’ subsumes very different notions, which depend on how the molecule and its components are conceived, and each of which brings its own difficulties. In particular, we will focus on how the molecule and its structure are devised from a classical view and from a quantum–mechanical view, and will discuss the different problems related with molecular structure that arise in each case.

分子结构的概念是化学中最重要的概念之一。事实上，分子结构与化学物质的概念及其一系列性质密切相关，是解释反应性的主要因素。事实上，物质的许多行为都是用其组成分子的结构来解释的。这可以解释为什么人们倾向于认为分子结构的概念是理所当然的。然而，当谈到具体概念时，问题就已经开始了，因为没有对所有化学都有效的“分子结构”的明确定义。本文的目的是表明“分子结构”一词包含非常不同的概念，这些概念取决于分子及其成分的构思方式，并且每个概念都有其自身的困难。特别是，我们将重点关注如何从经典观点和量子力学观点设计分子及其结构，并将讨论每种情况下出现的与分子结构相关的不同问题。