Text 15

( - 3 ). The Bohr Theory of the Hydrogen Atom

Most our knowledge of the electronic structure of atoms has been obtained by the study of the light given out by atoms when they arc excited by high temperature or by an clcctric arc or spark. The light that is emitted by atoms of a given substancc can be rcfractcd or diffractcd into a distinctive pattern of lines of certain frequencies; such a distinctive pattern of lines is said to be the line spectrum of the atom.

The careful study of line spectra began about 1880. Early investigators made some progress in the interpretation of spectra, in recognizing regularities in the frequencies of the lines: the frequencies of the spectral lines of the hydrogen atom, for example, show an especially simple relationship with one another. It was not until 1913 however, that the interpretation of the spectrum of hydrogen in terms of the clcctronic structure of the hydrogen atom was achieved. In that year, die Danish physicist Niels Bohr (1885-1962) successfully applied the quantum theory to this problem, and laid the basis for the extraordinary advance in our understanding of the nature of matter that has been made since then.

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1. There was only one atomic theory in the history of chemistry. 2. The light that is emitted by atoms of a given substancc gives a distinctive pattern. 3. The line spectrum is the spectrum of an atom but not a molcculc. 4. The result of early investigations was that the line spcctra of the hydrogen atom were not alike. 5. Niels Bohr was not interested in studying spcctral lines. 6. The application of the quantum theory helped to understand the electronic structure of the hydrogen atom better.

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Section 1

Ex. 1. Respond to the following requests and invitations. Use the expressions: with pleasure, here you are, certainly, of course.

1. Shall we go to the University together? 2. Give me your textbook for some days, please. 3. Will you help me to do the exercise? 4. Please bring me my notebook, you'll find it on the table. 5. Let's spend Sunday together. 6. Let's go for a walk after finishing our homework. 7. Have you been to the Russian Museum? Let's go there with Mary, she knows a lot about Russian art. 8. Could you show mc the way to the laboratory of organic chemistry, please?

Ex. 2. Translate the sentences into English.

Model: -An alternative question. - An answer

1. ϳ ? - . 2. , , . - . 3. , . - . 4. ? -. 5. , ? - . 6. . - . 7. , . - .

Ex. 3. Make up short dialogues according to the model. Modi

Example:

- Arc you a student or a post-graduate?

- I'm a student.

Ex. 4. Give detailed answers to the following questions:

1. What kind of particle is callcd an atom? 2. What was Dalton's idea of ??an atom? 3. What is the difference between Dalton's and modern theory

of the atomic structure? 4. In what way did Bohr's work develop the atomic theory? 5. What relationship is there between an atom and its spectrum?

Ex. 5. Discuss the following topics:

1. The Evolution of the Atomic Theory.

2. The Modem Concept of die Composition and Structure of an Atom.

3. The Basis for Spectral Analysis.

WHAT IS IT?

An optical instrument for forming and examining spectra.




Text 9 | Fluorine | Lesson 10 | Text 10 | Lesson 11 | Fascinating Phosphorus | Modifications of Phosphorus | Lesson 12 | Chemical Symbols for Representing Compounds | Weight of 12 atom of carbon 12 |

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