These elements, unlike the transition elements, do not exhibit variable oxidation states, and their valence electrons are only present in their outer shell.
这些元素，不像过渡金属那样显示出可变的化合价，他们只有最外层电子参加反应。
Step three in our Lewis structure rules is to figure out how many electrons we would need in order for every single atom in our molecule to have a full valence shell.
路易斯结构规则的第三步是，找出让分子中每个原子的价壳层，都排满应该需要多少个价电子。
Halogen atoms contain seven electrons in their valence shell, and, consequently, are monovalent.
卤原子在它们的价电子层含有七个电子，因此是一价的。
Halogen atoms contain seven electrons in their valence shell, and, consequently, are monovalent.
卤原子在它们的价电子层含有七个电子，因此是一价的。
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