The letters H-E-P-A represent the words High Efficiency Particulate Air.

VOA: special.2009.07.14

Well, we would have to H+ have one of these hydrogen atoms go to an H plus, * plus an electron, right? **H --> H+ + e-** So, now we have a hydrogen ion here.

我们先要让,一个氢原子变成氢离子，加上一个电子，对么*,我们现在有一个氢离子了。

麻省理工公开课 - 固态化学导论课程节选

E. E. Cummings, T. S. Eliot, W. H. Auden

. E. 康明斯、T. S. 艾略特、W. H. 奥登，

我的专业 - SpeakingMax英语口语达人

So we have s e h 2.

所以我们有SeH2。

麻省理工公开课 - 化学原理课程节选

H- *H + e-> H-* And, clearly, we can't do both.

到一个电子生成*,但我们发现我们不能同时做到两个。

麻省理工公开课 - 固态化学导论课程节选

So we can figure out the energy of each photon emitted by our UV lamp by saying e is equal to h c over wavelength.

所以我们可以计算出,每个从紫外光源射出的光子,也就是e等于h乘以c除以波长。

麻省理工公开课 - 化学原理课程节选

And there's actually a way that we can make predictions here, and what I'll tell you is molecular orbital theory predicts that h e 2 does not exist because it's not stabilized in terms of forming the molecule.

其实我们有一种办法可以做出预测，我要告诉你们的是分子轨道,理论预测He2不存在,因为它形成分子不稳定。

麻省理工公开课 - 化学原理课程节选

So our bond order for h e 2 is going to be equal to 0.

所以He2的键序等于0。

麻省理工公开课 - 化学原理课程节选

So it has a bond, there's no bond in h e 2.

所以在He2里没有键。

麻省理工公开课 - 化学原理课程节选

So what actually turns out the reality is that h e 2 does exist, but it exists as the weakest chemical bond known, and it wasn't, in fact, even found to exist until 1993, so I can assure you this is not a bond that you see very often in nature, and it is a very, very weak bond.

实际上He2键是存在的，但它是目前所知的最弱的键，直到1993年它才被发现，所以我可以向你们保证在,自然界你们不可能经常看到它，它是种非常非常弱得键。

麻省理工公开课 - 化学原理课程节选

So we can compare the two electron configurations, and we can actually think about what we figure out from them, we see that two are lowered in energy, two electrons are raised in energy, so we have no net gain or no net loss in energy for h e 2.

我们可以比较两种电子构型，我们可以考虑,我们发现这，两个电子能量变低，两个电子能量升高，所以在He2里没有净的能量得失。

麻省理工公开课 - 化学原理课程节选

- There are a few equations that you need to memorize -- those are the very simple -- very, very simple equations, such as e equals h times nu -- hopefully you don't have to sit down and try to memorize that, hopefully we all know that already.

只有几个公式是需要记住的-,它们都非常简单，非常非常简单，比如，E，等于，h，乘以，ν,希望大家不需要再专门去背了，希望我们已经都记住了。

麻省理工公开课 - 化学原理课程节选

Let's draw the molecular diagram for h e 2 now.

让我们画一下He2的分子图。

麻省理工公开课 - 化学原理课程节选

So the square root of n squared r e over r h.

这里的n值是什么呢？

麻省理工公开课 - 化学原理课程节选

Oh, E equals h nu. I will plug in.

哦，E=hv，我要算出来。

麻省理工公开课 - 固态化学导论课程节选