For the carbon, we start with 4 valence electrons, we have 0 lone pair electrons minus 4, and we end up with a formal charge of 0.

对于碳，我们从四个价电子开始，我们有零个孤对电子，再减去四，最终我们有零个形式电荷。

麻省理工公开课 - 化学原理课程节选

But we do have four seasons. You can see it on the tree.

但是我们确实有四个季节。你可以从树上看出来。

关于伦敦的天气 - SpeakingMax英语口语达人

Yeah, so also 4. We started with 10 valence electrons, we used up 6 of those as bonding electrons, so we have 4 left, which will be lone pair electrons.

对，也是四个，我们从十个价电子开始，只用了六个来成键，因此我们还剩下四个，它们将成为孤对电子。

麻省理工公开课 - 化学原理课程节选

So this is what he asked them to do: Select four answers to the question 'What should a reader be to be a good reader?' "The reader should belong to a book club."

这就是他要求学生们做的：,从以下四个选项中选取问题,“读者如何才能成为好读者”的答案：,“读者应该是书友会的成员“

耶鲁公开课 - 1945年后的美国小说课程节选

The total energy of the system, which we are going to get from postulate number four, which says the energy of the electron, which is the energy of the system, is the sum of the kinetic and the potential energy.

这个系统的总能量，也就是我们将从第四个假设中算出的能量，也就是电子运动产生的能量，也就是整个系统的能量，是动能和位能的总和。

麻省理工公开课 - 固态化学导论课程节选

You can say a polymer of DNA, for example, is four bases long, that means it has four of these repeat units and they go in the sequence from 5' to 3' of .

打个比方,要描述一个由,四个核苷酸单位构成的寡聚DNA,就是说它由四个核苷酸单位构成,并且从5'端到3'端的顺序为

耶鲁公开课 - 生物医学工程探索课程节选

For the sulfur, we start off with 6 valence electrons, minus 4 lone pair electrons, minus 2, taking in account our bonding electrons, so we end up with a formal charge of 0.

对于硫，我们从六个价电子开始，减去四个孤对电子，再减去二，算上我们的成键电子，因此最终我们有零个形式电荷。

麻省理工公开课 - 化学原理课程节选