6.1 An atomic model is needed to understand how atoms bond Electrons in the outermost occupied shell of any atom are responsible for the atoms chemical properties The electrons that participate in chemical bonding are called valence electrons(价电子) the shell they occupy is called the valence shell(价层) of an atom alence electrons can be conveniently represented as a series of dots surrounding an atomic symbol (Electron-dot structure or Lewis dot symbol) Valance electrons can be either paired or unpaired Paired electrons usually do not form chemical bonds with other elements6.1 An atomic model is needed to understand how atoms bond Electrons in the outermost occupied shell of any atom are responsible for the atom’s chemical properties. The electrons that participate in chemical bonding are called valence electrons (价电 子),the shell they occupy is called the valence shell (价层) of an atom. Valence electrons can be conveniently represented as a series of dots surrounding an atomic symbol. (Electron-dot structure or Lewis dot symbol). Valance electrons can be either paired or unpaired. Paired electrons usually do not form chemical bonds with other elements