So what we see is on ammonia here, 107 we know that it's less than a 109 . 5, it's actually 107, so it's less than a 109 . 5, because of that lone pair pushing down in the bonding electrons.

我们看到在氨分子里，我们知道它比１０９．５要小，它是，所以比109。5要小，因为孤对会把成键电子向下推。

麻省理工公开课 - 化学原理课程节选