When we talk about anti-bonding, 1sb essentially we're taking 1 s a and now we're subtracting 1 s b, sigma1s and what we end up with again is sigma 1 s, and the important thing to remember is to write this star here.

当我们讨论反键时，本质上我们是用1sa减去，最后我们得到，记住这里有个星。

麻省理工公开课 - 化学原理课程节选