It's also important, once we start talking about molecules, to have a way to represent them, and also to be able to look at a shorthand notation for a certain molecule and understand what the bond is.

还有很重要一点是，一旦我们开始讨论分子，我们需要有一种表示它们的方法，而且能够从中看出,某些分子的简化符号，并得知键的类型。

麻省理工公开课 - 化学原理课程节选

So, for example, 1s1 again we see hydrogen is 1 s 1, helium we say is 1 s 2, or 1 s squared, 1s2 so instead of writing out the 1 s 1 and the 1 s 2, we just combine it 1s22s1 as 1 s squared, lithium is 1 s 2, 2 s 1.

简化符号所以举例来说，我们又看到氢是，氦是1s2或者1s的平方，所以不是将它写为1s1和1,而是我们将它合并为1s的平方,锂是。

麻省理工公开课 - 化学原理课程节选