So, let's go back to the notes, and let's fill these in, seven electrons. Another way you could have known them was to look at Lewis' notes here, where if look at this box carefully you see there are seven dots around the cube, so there are his seven valence electrons.

那么，让我们回到讲义，把它们填进去，七个电子，还有另外一种方法可以知道这些,那就是看看路易斯的讲义这里，大家可以看到这个立方体周围有七个点,因此有七个价电子。

麻省理工公开课 - 化学原理课程节选