the deflection of the alpha particle through large angles and even bouncing off the gold foil you must keep in mind that the gold nuclei have a charge of +79 and the alpha particle has a charge of +2. These two positive charges repel each other. The closer they get, the greater the force. The greater the force, the greater the amount of deflection.
While the Rutherford model focused on describing the nucleus, Niels Bohr turned his attention to describing the electron. Prior to the Bohr Model, the accepted model was one which depicted the electron as an orbiting planet. The flaw with the planet-like model is that an electron particle moving in a circular path would be accelerating. An accelerating electron creates a changing magnetic field. This changing magnetic field would carry energy away from the electron, eventually slowing it down and allowing it to be “captured” by the nucleus.
Bohr built upon spectroscopic observations of atoms. Spectroscopists noticed that an atom can only absorb certain energies (colors) of light (the absorption spectrum) and, once excited, can only release certain energies (the emission spectrum) and these energies happen to be the same. Bohr used these observations to argue that the energy of a bound electron is “quantized.” Quantized is a fancy word meaning only certain quantities of energy are allowed. This explanation addresses the true . Since only certain energy levels are allowed, it is actually possible to diagram the atom in terms of its energy levels. In the figure below you see a model of a Hydrogen atom and to the right of it, a Bohr energy level diagram.
The Hydrogen Atom
If the energy of the photon of light is just right, it will cause the electron to jump to a higher level. When the electron jumps back down, a photon is created for each jump down. A photon without the right amount of energy passes through the atom with no effect. Photons with too much energy will cause the electron to be ejected, which ionizes the atom. An ionized electron is said to be in the n=infinity energy level. Keep in mind that these rings are not actually orbits, but are levels that represent the location of an electron wave. The number n corresponds to the number of complete waves in the electron.
Ex. 1. Make the following sentences negative.
1. We will limit our discussions to protons, neutrons and electrons. 2. Protons and neutrons are believed to be made up of even smaller particles called quarks. 3. The electrons actually change their orbit with each revolution. 4. Quantized is a fancy word meaning that only certain quantities of energy are allowed. 5. The number n corresponds to the number of complete waves in the electron.
Ex. 2. Make up questions to which the following sentences are the answers.
1. Photons with too much energy will cause the electron to be ejected which ionizes the atom. 2. The number n corresponds to the number of complete waves in the electron. 3. He developed the probability function for the Hydrogen atom. 4. The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. 5. The nucleus is made up of positively charged particles called protons and neutrons which are neutral. 6. Prior to the Bohr Model, the accepted model was one which depicted the electron as an orbiting planet.
Ex. 3 Translate the sentences using the examples given below.
The institute installed modernized equipment. В институте установлено модернизированное оборудование. The equipment installed modernized our laboratory too. Установленное оборудование модернизировало и нашу лабораторию.
A. 1. The Conference attended by scientists from different countries discussed new trends and methods in this field of research. 2. One of the rights enjoyed by University scientists is that of combining research with teaching. 3. The discovery followed by further experimental work stimulated research in this area.
B. 1. Mathematics, mechanics, statics and geometrical optics referred to as classical disciplines started mathematical traditions in the history of natural science. 2. The heads of the laboratories were asked questions formulated and agreed upon by a group of sociologists. 3. The scientist's eloquence substituted for logical argu-entation in defending an “extreme” viewpoint failed to win the audience. 4. The mixture allowed to stay overnight gradually decomposed. 5. Physicists showed that particles thought of as “elementary” were in fact “non-elementary”. 6. The subjects dealt with under this topic aroused a heated discussion.
Ex. 4. Identify the structures including what and give Russian equivalents of the relevant part of the sentence.
1. What is done cannot be undone. 2. I would here refer to what I have already said about these substances. 3. This article will review what has been achieved in this field since 1981. 4. From what has been said one concludes that the results obtained depend principally on the technique employed. 5. What we want to stress is indivisibility and complexity of the environment. 6. What follows is extremely significant in its bearing on the problem of the relationship of physics with other sciences. 7. Much of what we do in space, much of what is expected of us strains our technology to the breaking point. 8. In this article Dyson states what may be considered three rules of managing a research laboratory. 9. What goes into a system must eventually come out.
Ex. 5. Learn to distinguish between modal and auxilliary to have and to be. State their function and give Russian equivalents.
1. The argument is that by that time the resources of the plane may have been exhausted and man may have had to leave the Earth in search for another habitable place. 2. To get anywhere and back in a lifetime the speed would have to be very high so as to take advantage of the relativistic change in clock rates. 3. The maximum value which is to be expected is only reached in the range of variables used in the tests. 4. If Mars were a testing ground for our notion about the origin of life, we must avoid using the same notion to conclude in advance that Mars is lifeless. 5. As it is true of the author, we have had to be a little arbitrary in deciding what to include and what to omit. 6. If we built a scale model with the Earth as a ball 100 feet in diameter, this ocean would be less than half an inch deep.
The Cloud Model
Erwin Schredinger built upon the thoughts of Bohr yet took them in a new direction. He developed the probability function for the Hydrogen atom (and a few others). The probability function basically describes a cloudlike region where the electron is likely to be found. It cannot say with any certainty, where the electron actually is at any point in time, yet can describe where it ought to be. Clarity through fuzziness, is one way to describe the idea. The model based on this probability equation can best be described as the cloud model.
The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. The red dot in the middle represents the nucleus while the red dot around the outside represents an instance of the electron. Imagine, as the electron moves it leaves a trace of where it was. This collection of traces quickly begins to resemble a cloud. The probable locations of the electron predicted by Schredinger's equation happen to coincide with the locations specified in Bohr's model.
What is an atom composed of?
