听力原文:W: Good morning, sir. Can I help you? M: Yes. Can I check out now? I'm leaving an hour later. My name is George Brown and my Room Number is 2009. Q: Where does this conversation most probably take place? (3)
【简答题】Although there is no sharp boundary that defines the outside of an atom or ion, we can think of the size of the atom as the volume containing about 90% of the total electron density around the nucleus...