Section outline

  • General

    Collapse all Expand all

  • 黄金焦油实验

    Close-up view of a brick wall showing the texture and arrangement of bricks.

    How much space do bricks occupy?
    ::砖头占用多少空间?

    As we look at the world around us, it looks pretty solid.  We hit a wall with our hand and the hand stops – it does not (normally) go through the wall.  We think of matter as occupying space.  But there is a lot of empty space in matter.  In fact, most of the matter is empty space.
    ::当我们观察周围的世界时,它看起来相当坚固。我们用手撞墙和手停下,它不会(通常)穿过墙。我们认为物质是占据空间。但这里有很多空地。事实上,大部分是空地。

    The Gold Foil Experiment
    ::Gold Fooil 实验

    In 1911, Rutherford and coworkers Hans Geiger and Ernest Marsden initiated a series of groundbreaking experiments that would completely change the accepted model of the . They bombarded very thin sheets of gold foil with fast moving alpha particles . Alpha particles, a type of natural radioactive particle, are positively charged particles with a mass about four times that of a hydrogen atom.
    ::1911年,卢瑟福和同事汉斯·盖格和欧内斯特·马尔斯登发起了一系列突破性实验,将彻底改变公认的模型。他们用快速移动的阿尔法粒子轰炸了非常薄的金宝石板。 阿尔法粒子是一种天然放射性粒子,其质量是氢原子的四倍。

    Experimental setup of Rutherford's gold foil experiment showing alpha particles striking gold foil.

    (A) The experimental setup for Rutherford's gold foil experiment: A radioactive element that emitted alpha particles was directed toward a thin sheet of gold foil that was surrounded by a screen which would allow detection of the deflected particles. (B) According to the plum pudding model (top) all of the alpha particles should have passed through the gold foil with little or no deflection. Rutherford found that a small percentage of alpha particles were deflected at large angles, which could be explained by an atom with a very small, dense, positively-charged nucleus at its center (bottom).
    :sadA) 卢瑟福的金粉实验实验实验的实验设置:一个释放α粒子的放射性元素被射向一个薄的金粉板,环绕着一个屏幕,可以探测偏向的粒子。 (B)根据梅子布丁模型(顶部),所有α粒子都应在很少或没有偏向的情况下穿过金粉。露瑟福发现,一小部分α粒子被大角度偏向,这可以用一个原子在中心(底部)有一个非常小、密度大、弹源正核的原子来解释。

    According to the accepted atomic model , in which an atom's mass and charge are uniformly distributed throughout the atom, the scientists expected that all of the alpha particles would pass through the gold foil with only a slight deflection or none at all. Surprisingly, while most of the alpha particles were indeed undeflected, a very small percentage (about 1 in 8000 particles) bounced off the gold foil at very large angles. Some were even redirected back toward the source. No prior knowledge had prepared them for this discovery. In a famous quote, Rutherford exclaimed that it was "as if you had fired a 15-inch [artillery] shell at a piece of tissue paper and it came back and hit you."
    ::根据公认的原子模型,原子质量和电荷在整个原子中均匀分布,科学家们预计所有阿尔法粒子都会通过金宝石,只有轻微的偏转或完全没有。 令人惊讶的是,尽管大多数阿尔法粒子的确没有被忽略,但很小比例(大约8000颗粒子中有1个)在非常大的角度从金宝石上跳下来。有些人甚至被重新引导回到了源头。事先没有知识为发现这些粒子做准备。在著名的引言中,露瑟福德说这是“就像你在纸纸上发射了15英寸[炮 炮弹一样,它又回到了你身上。 ”

    Rutherford needed to come up with an entirely new model of the atom in order to explain his results. Because the vast majority of the alpha particles had passed through the gold, he reasoned that most of the atom was empty space. In contrast, the particles that were highly deflected must have experienced a tremendously powerful force within the atom. He concluded that all of the positive charge and the majority of the mass of the atom must be concentrated in a very small space in the atom's interior, which he called the nucleus . The nucleus is the tiny, dense, central core of the atom and is composed of and neutrons.
    ::卢瑟福需要找到一个全新的原子模型来解释他的结果。由于绝大多数的α粒子都穿过金块,他推理说大部分原子都是空的。相反,高度偏转的粒子在原子中必然经历了巨大的力量。他的结论是,所有正电荷和原子大部分质量必须集中在原子内部一个很小的空间里,他称之为核。核核是原子的微小、稠密、核心核心,由中子组成。

    became known as the nuclear model . In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. The electrons are distributed around the nucleus and occupy most of the volume of the atom. It is worth emphasizing just how small the nucleus is compared to the rest of the atom. If we could blow up an atom to be the size of a large professional football stadium, the nucleus would be about the size of a marble.
    ::在核原子中,质子和中子几乎构成原子的所有质量,位于原子中心的核心。电子分布在核核心,占据了原子的大部分。值得强调的是核与原子的其余部分相比小得多。如果我们能将原子炸成一个大型专业足球场的大小,核心就相当于大理石。

    Rutherford's model proved to be an important step towards a full understanding of the atom. However, it did not completely address the nature of the electrons and the way in which they occupied the vast space around the nucleus. It was not until some years later that a full understanding of the was achieved. This proved to be the key to understanding the chemical properties of .
    ::卢瑟福的模型证明是全面了解原子的一个重要步骤,但它没有完全解决电子的性质及其占据核心周围广阔空间的方式,直到几年后才完全了解原子,这证明是了解原子化学特性的关键。

     

     

     Summary
    ::摘要

    • Bombardment of gold foil with alpha particles showed that  a very small percentage of alpha  particles were deflected.
      ::用阿尔法粒子轰炸金表明,极小比例的阿尔法粒子被偏转。
    • The nuclear model of the atom consists of a small and dense positively charged interior surrounded by a cloud of electrons.  
      ::原子的核模型由一小块由一团电子云环绕而成的 密密而实心充电的内部组成。

    Review  
    ::回顾

    1. What is an alpha particle?
      ::什么是阿尔法粒子?
    2. What did Rutherford observe from shooting thousands and thousands of alpha particles at a thin piece of gold foil?
      ::卢瑟福从射杀成千上万个阿尔法粒子 在一个薄薄的金宝石上观察到什么?
    3. How did Rutherford explain the observation that most alpha particles went straight through the gold foil?
      ::卢瑟福如何解释 大部分的阿尔法粒子 直接穿过金宝石的观察?
    4. What did he say about the particles that were deflected?
      ::他对被偏转的粒子说了什么?
    5. Describe Rutherford’s nuclear model.
      ::描述卢瑟福的核模式。