Positive energy is repulsive, and negative energy is attractive.

正的能量值代表斥力，负的能量值代表引力。

麻省理工公开课 - 固态化学导论课程节选

We know that binding energy is always negative, ionization energy is always positive.

我们知道结合能，总是负的，电离能总是正的。

麻省理工公开课 - 化学原理课程节选

putting all those things together, if you looked at this question again we'd get 100% on it, 0 9 that our only option here is 0. 9, and that it's not the negative, it's the positive version, because we're talking about how much energy we have to put into the system in order to eject an electron.

把这些放在一起，你们再看一下题目,大家100%都能选对，我们唯一的选择就是这个，它不是负数，它是正的，因为我们说的，是要,把电子激发出来,需要提供的能量。

麻省理工公开课 - 化学原理课程节选

So you don't want to put in a negative energy, that's not going to help you out, you need to put in positive energy to get an electron out of the system. So that's why you'll find binding energies are always negative, and ionization energies are always going to be positive, or you could look at the equation and see it from there as well.

因为这对电离没有帮助,你需要一个正的能量,使得电子脱离这个系统,这就是为什么你会发现,结合能总是负的而电离能总是正的,或者你们看这个方程也可以发现这一点。

麻省理工公开课 - 化学原理课程节选