英语听力文摘493 惨淡的人生
Don: A guy walks into a bar, and sits down next to an electron. The electron has two empty beers in front of him, and was working on a third. "My life is a worst", says electron. "I just got fired from my job, my dog bit me, my wife left with another guy." The guy says, "Why are you so negative?"
OK, now the explanation. The nucleus of an atom is composed of neutrons and protons. Around this nucleus swirls a cloud of electrons. Why are the electrons there? They are attracted and held in place by an electromagnetic interaction with the nucleus. The nucleus has a net positive charge, while electrons carry a negative charge. And opposite charges attract.
Yaël: I get it! "Why so negative?" He's talking to an electron.
D: Right!
Y: So electrons have a negative charge, while protons, neutrons and nucleus have a positive charge?
D: Almost! The protons have the positive charge, while the neutrons, as their name suggests, have no charge at all. If you have three protons in the nucleus, you'll need three electrons to make what's called a "stable" atom.
原子核
Don: 有一个人走进了酒吧，刚刚好坐在了电子的旁边。电子面前已经摆了两个空啤酒瓶子了，正在与他的第三瓶“奋战”着。“我的生活真的很糟糕”电子说道，“我刚刚被公司辞退了，我的狗要咬我，老婆也和别的男人跑了!”这个人问道：“你为什么这么negative呢?”
(注：negative通常情况下是表示“消极的，负面的”，而此处不做此用。此处，negative应理解为“带负电的，阴性的”)
OK，现在来解释一下。原子核由中子和质子两种微粒构成。在原子核外部，电子云围绕原子核旋转。为什么这里会有电子呢?电子通过与原子核的电磁相互作用，被吸引到了这里。原子核带正电荷，而电子则带负电荷。而我们知道，异性相吸。
Yaël: 我懂了。“谁叫你带负电呢?”他对电子说的话应该是这样理解的吧。
D: 是的。
Y: 那么，也就是说电子是带负电荷，而质子、中子和原子核都是带正电荷?
D: 这样说也差不多!质子是带正电荷的，而中子就像他的命名所暗示的一样，是不带点的。如果一个原子核中有三个质子，那么必须要有三个电子，这个原子才能够称得上是“稳定的”原子。
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