3.14 卢瑟福的原子能模型
章节大纲
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Thom is shooting baskets. He’s trying to hit the backboard so the ball will bounce off it and into the basket. If only the backboard was bigger! It would be a lot easier to hit. If the ball misses the backboard, it will just keep going and Thom will have to run after it. Believe it or not, the research that led to the discovery of the nucleus of the was a little like shooting baskets.
::托姆正在拍摄篮子。 他试图敲打后板,让球弹出并进入篮子中。 如果只有后板更大的话, 击球会更容易得多。 如果球漏掉后板, 球就会继续前进, 托姆将不得不追逐它。 信不信由你, 导致发现球核心的研究就像射击篮子一样。Narrowing Down the Nucleus
::缩小核心In 1804, almost a century before the nucleus was discovered, the English scientist John Dalton provided evidence for the existence of the atom. Dalton thought that atoms were the smallest particles of matter, which couldn't be divided into smaller particles. He modeled atoms with wooden balls. In 1897, another English scientist, named J. J. Thomson, discovered the . It was first subatomic particle to be identified. Because atoms are neutral in electric charge , Thomson assumed that atoms must also contain areas of positive charge to cancel out the negatively charged electrons. He thought that an atom was like a plum pudding, consisting mostly of positively charged matter with negative electrons scattered through it.
::1804年,在核发现前近一个世纪,英国科学家约翰·道尔顿提供了原子存在的证据。道尔顿认为原子是物质中最小的粒子,不能分成较小的粒子。他用木球模拟原子。1897年,另一位英国科学家J.J.汤姆森发现了这个原子。这是第一个需要识别的亚原子粒子。由于原子在电荷中是中性的,汤姆森认为原子必须包含积极电荷,才能消除负电荷电子。他认为原子就像根梅布丁,大部分由阴性电荷物质组成,散落在其中。The nucleus of the atom was discovered next. It was discovered in 1911 by a scientist from New Zealand named Ernest Rutherford, who is pictured in Figure . Through his clever research, Rutherford showed that the positive charge of an atom is confined to a tiny massive region at the center of the atom, rather than being spread evenly throughout the “pudding” of the atom as Thomson had suggested.
::原子的核心于1911年被新西兰科学家欧内斯特·卢瑟福(Ernest Rutherford)所发现,他在图中描绘。 路瑟福(Lutherford)通过他的聪明研究显示,原子的正面作用仅限于原子中心一个很小的面积,而不是像汤姆森所说的那样,在原子“铺设”整个“铺设”时均匀分布。Go for the Gold!
::向金子进发!The way Rutherford discovered the is a good example of the role of creativity in science . His quest actually began in 1899 when he discovered that some give off positively charged particles that can penetrate just about anything. He called these particles alpha (α) particles (we now know they were helium nuclei). Like all good scientists, Rutherford was curious. He wondered how he could use alpha particles to learn about the structure of the atom. He decided to aim a beam of alpha particles at a sheet of very thin gold foil. He chose gold because it can be pounded into sheets that are only 0.00004 cm thick. Surrounding the sheet of gold foil, he placed a screen that glowed when alpha particles struck it. It would be used to detect the alpha particles after they passed through the foil. A small slit in the screen allowed the beam of alpha particles to reach the foil from the particle emitter. You can see the setup for Rutherford’s in the Figure .
::卢瑟福发现这是科学中创造力作用的一个很好的例子。 他的研究实际上始于1899年,当时他发现某些粒子会释放出能够渗透到任何事物的有积极电粒子。他称这些粒子阿尔法粒子(α)粒子(我们现在知道它们是核 ) 。 和所有优秀的科学家一样,卢瑟福很好奇。他想知道他如何能够利用α粒子了解原子的结构。他决定用非常薄的金质板来瞄准一个α粒子束。他选择黄金,因为它可以被挤到只有0.0004厘米厚的床单上。在金质板上,他放置了一张在α粒子击中时发光的屏幕。当这些粒子穿过烟雾时,它将用来检测α粒子。屏幕上的一小片细片使得α粒子能够从粒子发射者那里接触到灰尘。你可以看到图中卢瑟福的图案。Q: What would you expect to happen when the alpha particles strike the gold foil?
::问:当阿尔法粒子击中金质封状时,你会期待会发生什么?A: The alpha particles would penetrate the gold foil. Alpha particles are positive, so they might be repelled by any areas of positive charge inside the gold atoms.
::A: 阿尔法粒子会穿透金质。 阿尔法粒子是正的, 所以它们可能会被金原子内任何正充电区击退 。Assuming a plum pudding model of the atom, Rutherford predicted that the areas of positive charge in the gold atoms would deflect, or bend, the path of all the alpha particles as they passed through. You can see what really happened in the Figure . Most of the alpha particles passed straight through the gold foil as though it wasn’t there. The particles seemed to be passing through empty space. Only a few of the alpha particles were deflected from their straight path, as Rutherford had predicted. Surprisingly, a tiny percentage of the particles bounced back from the foil like a basketball bouncing off a backboard!
::卢瑟福(Lutherford)假设是原子的梅布布丁模型,他预测金原子中正充电区会偏转或弯曲所有阿尔法粒子经过的路径。你可以看到图中的真实情况。大部分阿尔法粒子直接穿过金质堆,好像没有。这些粒子似乎正在穿过空地。只有少数阿尔法粒子偏离了直路,正如卢瑟福预测的那样。令人惊讶的是,微小一部分的粒子像篮球从后板上跳动一样从叶子中反弹回来!Q: What can you infer from these ?
::问:你能从中得出什么结论?A: You can infer that most of the alpha particles were not repelled by any positive charge, whereas a few were repelled by a strong positive charge.
::甲:可以推断,大部分α粒子没有被任何正电荷击退,而少数粒子被强烈正电荷击退。The Nucleus Takes Center Stage
::" 核心 " 核心阶段Rutherford made the same inferences. He concluded that all of the positive charge and virtually all of the mass of an atom are concentrated in one tiny area and the rest of the atom is mostly empty space. Rutherford called the area of concentrated positive charge the nucleus. He predicted—and soon discovered—that the nucleus contains positively charged particles, which he named . Rutherford also predicted the existence of neutral nuclear particles called , but he failed to find them. However, his student James Chadwick discovered them several years later.
::他的结论是,所有正电荷和原子的几乎所有质量都集中在一个很小的地区,而原子的其余部分大部分是空的。卢瑟福称集中正电荷区为核。他预测 — — 并很快发现 — — 核中含有有积极电荷的粒子。 卢瑟福也预测了中立核粒子的存在,但没能找到这些粒子。然而,他的学生詹姆斯·查德维克在几年后发现了这些粒子。The Planetary Model
::行星模型Rutherford’s discoveries meant that Thomson’s plum pudding model was incorrect. Positive charge is not spread evenly throughout an atom. Instead, it is all concentrated in the tiny nucleus. The rest of the atom is empty space except for the electrons scattered through it. In Rutherford’s model of the atom, which is shown in the Figure , the electrons move around the massive nucleus like planets orbiting the sun. That’s why his model is called the planetary model. Rutherford didn’t know exactly where or how electrons orbit the nucleus. That research would be undertaken by later scientists, beginning with Niels Bohr in 1913. New and improved atomic models would also be developed. Nonetheless, Rutherford’s model is still often used to represent the atom.
::卢瑟福的发现意味着汤姆森的梅布布布丁模型是不正确的。 正面电荷在整个原子中分布不均匀。 相反,它都集中在小核中。 原子的其余部分是空空间,除了通过它散布的电子之外。 在图中显示的卢瑟福的原子模型中,电子在巨型核周围移动,就像绕着太阳运行的行星一样。 这就是为什么他的模型被称为行星模型。 卢瑟福并不确切知道电流绕着核的去向或如何绕过核。 这一研究将由后来的科学家进行,从1913年的尼尔斯·博尔开始。 新的和改良的原子模型也将得到开发。 尽管如此,卢瑟福的模型仍然经常被用来代表原子。Summary
::摘要-
Ernest Rutherford discovered the nucleus of the atom in 1911. He sent a beam of alpha particles toward gold foil and observed the way the particles were deflected by the gold atoms. From his results, he concluded that all of the positive charge and virtually all of the mass of an atom are concentrated in one tiny area, called the nucleus, and the rest of the atom is mostly empty space.
::欧内斯特·卢瑟福在1911年发现了原子的核心。 他将一束阿尔法粒子射向金质,并观察了这些粒子被金质原子转移的方式。 从他的研究结果中,他得出结论,所有正电荷和几乎所有原子的质量都集中在一个小小的地区,叫做核,而原子的其余部分则大多是空空的。 -
In Rutherford’s planetary model of the atom, the electrons move through empty space around the tiny positive nucleus like planets orbiting the sun.
::在卢瑟福的行星原子模型中,电子在空空空间中移动,围绕微小的正核,如绕着太阳运行的行星。
Review
::回顾-
How did Ernest Rutherford discover the nucleus of the atom?
::欧内斯特·卢瑟福是怎么发现原子核心的? -
Place Rutherford’s discovery in the broader history of the atom.
::将卢瑟福的发现 放在原子的更广阔历史中。 -
Describe how you could make a three-dimensional version of Rutherford’s planetary model of the atom.
::描述你如何能制作出 卢瑟福的行星模型的三维版本。
Explore More
::探索更多Watch this video about Rutherford’s gold foil experiment, and then answer the questions below.
::观看关于卢瑟福金宝石实验的影片, 然后回答下面的问题。-
How did Rutherford observe alpha particles in his experiment? In the modern version of Rutherford’s experiment, which is shown in the video, how are alpha particles observed? Which way do you think is more accurate?
::卢瑟福在实验中如何观察阿尔法粒子?在视频中展示的卢瑟福实验的现代版本中,如何观察阿尔法粒子?你认为哪一种方法更准确? -
Based on the animation in the video, draw a sketch showing what happens to alpha particles as they pass through gold atoms.
::根据视频中的动画,绘制一张草图,显示阿尔法粒子穿过金原子时发生的情况。 -
How has Rutherford’s gold foil experiment been adopted by modern researchers?
::现代研究人员如何采用卢瑟福的金宝石实验?
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Ernest Rutherford discovered the nucleus of the atom in 1911. He sent a beam of alpha particles toward gold foil and observed the way the particles were deflected by the gold atoms. From his results, he concluded that all of the positive charge and virtually all of the mass of an atom are concentrated in one tiny area, called the nucleus, and the rest of the atom is mostly empty space.
