So if we do this and we form the molecule ammonia, let's switch to a clicker question, and have you tell me what the bond angle - is going to be in ammonia -- HNH Actually, let me draw it on the board as you look -- actually, can you put the class notes on, since you don't actually have your notes to refer to.

如果这样做的话，我们就可以形成氨分子，让我们来做一个课堂练习,你们告诉我氨分子中的键角是多少-,键角，the，h，n，h，bond，angle。,实际上让我在黑板上画出它来，这样你们可以看到实际上-,你能把课堂讲义放出来吗，因为你们没有讲义可以参考。

化学原理课程节选 : 麻省理工公开课