英語聽力文摘493 慘淡的人生
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: 有一個人走進了酒吧，剛剛好坐在了電子的旁邊。電子面前已經擺了兩個空啤酒瓶子了，正在與他的第三瓶“奮戰(zhàn)”著。“我的生活真的很糟糕”電子說道，“我剛剛被公司辭退了，我的狗要咬我，老婆也和別的男人跑了!”這個人問道：“你為什么這么negative呢?”
(注：negative通常情況下是表示“消極的，負面的”，而此處不做此用。此處，negative應理解為“帶負電的，陰性的”)
OK，現(xiàn)在來解釋一下。原子核由中子和質子兩種微粒構成。在原子核外部，電子云圍繞原子核旋轉。為什么這里會有電子呢?電子通過與原子核的電磁相互作用，被吸引到了這里。原子核帶正電荷，而電子則帶負電荷。而我們知道，異性相吸。
Yaël: 我懂了。“誰叫你帶負電呢?”他對電子說的話應該是這樣理解的吧。
D: 是的。
Y: 那么，也就是說電子是帶負電荷，而質子、中子和原子核都是帶正電荷?
D: 這樣說也差不多!質子是帶正電荷的，而中子就像他的命名所暗示的一樣，是不帶點的。如果一個原子核中有三個質子，那么必須要有三個電子，這個原子才能夠稱得上是“穩(wěn)定的”原子。
