Notes on the Text

1. In the case of uranium — если мы имеем дело с ураном (в случае с

ураном)

2. Regular atoms — обычные атомы

3. To be of great significance — иметь большое значение

The word “isotope” is derived from the Greek “isos”, “topos” and means the same place.

Hence, isotopes are atoms having the same atomic number, but differing in atomic weight (mass number), e.g. and ²JC are isotopes of carbon, or one out of every 5,000 atoms of hydrogen has an atomic weight of 2.016 instead of 1.008.

This odd atom has a neutron in its nucleus as well as a proton, it being known as heavy hydrogen. The water contain­ing it is known as heavy water.

Isotopes occur with considerably greater frequency in other elements than in hydrogen, an extreme case being chlorine, its atomic weight being 35.5. It is made up of two groups of atoms in a ratio of 3 : 1, the weight of one group being 35, that of the other 37.

In the case of uranium, for example, one isotope of atomic weight 235 is found in every 140 atoms of the standard weight, with the weight being 238.

The chemical properties of isotopes being identical with those of regular atoms, their discovery was of little interest to chemists. Physicists, however, got interested in them, a new way of approaching to the structure of matter being opened.

Radioactive and Stable Isotopes

The use of new atomic power sources of tremendous ener­gies is of great significance.

However, a part of no lesser importance is played by radio­active and stable isotopes obtained in nuclear reactors and accelerators, almost every chemical element having a number of isotopes.

At present about 1,000 artificial radioactive isotopes emit­ting alpha, beta and gamma rays, and about 300 stable (i.e. non-emitting) isotopes of all elements of Mendeleyev’s Pe­riodic System are known.

Production of artificial radioactive isotopes has developed into a new industry, while their application has become so wide and diverse that one can hardly name a branch where they are not or cannot be used.

Thus when used by doctors, radiation of radioactive iso­topes is instrumental in diagnosing and curing diseases. When used by scientists they are helpful in penetrating into the deepest secrets of some processes.

Biologists have succeeded in breeding new varieties of microorganisms producing large quantities of most valuable antibiotics.

By using isotopes the control of the pig-iron and steel production process can be made simpler and cheaper.

By means of isotopes it is possible to control the extent of wear of cutting tools of machine parts while in operation with­out stopping or dismantling them. All this gave rise to new investigations of still more new uses of isotopes.

Remember the following words:

to derive	source
derivative	to accelerate
extreme	accelerator
to make up	to succeed
identical	pig-iron
diverse	by means of
regular	extent
to approach	to give rise to

Ex. 6. Answer the following questions:

1. What is an isotope? 2. What is heavy hydrogen?

3. What is heavy water? 4. What is the atomic weight of chlo­rine? 5. How many artificial radioactive isotopes are known at present? 6. What has production of artificial radioactive isotopes developed into? 7. What is possible to do by means of isotopes?

Ex. 7. Translate the following sentences:

Note: to give — давать

to give off — выделять, испускать to give out — выделять, выпускать to give attention to — уделять внимание to give rise to — вызывать, обусловливать, при­водить к

to give up — отказаться, оставить, бросить, уступить

1. Р. N. Yablochkov gave up a military career for the sake of science. 2. He has given me some interesting new books on chemistry. 3. Our scientists give much attention to the crea­tion of new types of cyclotrons. 4. Upon heating the substance was giving off harmul vapours. 5. His numerous experiments gave rise to new discoveries in the field of radioactive sub­stances. 6. The radiant energy can be given off in the form of photons. 7. The amount of energy given out during the forma-

2. tionof a nucleus from protons and neutrons is called the bind­ing energy of the nucleus.

Ex. 8. Find the pairs of antonyms and remember them:

seldom, odd, artificial, even, irregular, natural, regular,

unstable, possible, stable, impossible, frequently.

Ex. 9. Open the brackets choosing a suitable word:

1. Isotopes occur more (seldom, frequently) in other elements than in hydrogen.

2. The chemical properties of isotopes are (different, identical) with those of regular atoms.

3. At present about 1,000 (natural, artificial) radioactive isotopes are known.

4. The (even, odd) atom has a neutron in the nucleus as well as a proton.

5. The use of new atomic power sources of (tremendous, small) energies is of great significance.

6. Using isotopes it is possible to make the control of pig-iron and steel production process (cheaper, more expensive).

Ex. 10. Choose the Russian equivalents from the right column:

ускорять

частый

вес

частота приводить к ценный встречаться взвешивать

to occur frequency frequent weight to weigh to accelerate to give rise to valuable

Ех. 11. Give derivatives of the following words and translate them into Russian:

to consider; power; to accelerate; to produce; to use; to investigate.

Ex. 12. Translate the following sentences, mind the Absolute Participle Construction:

1. The experiment being very interesting, we work readily. 2. The range of application of stable isotopes being very wide, the scientists are interested in them. 3. The electron is about as large as a nucleus, its diameter being about lO"¹² cm. 4. Or­dinary salt being examined with a magnifying glass, they saw that the crystals were of cubic form. 5. A gas can be dissolved in a liquid, the liquid changing its boiling point. 6. The elements having been arranged in the Periodic Table, it became easier

to predict new elements. 7. The experiment being time-con­suming, he has to spend much time in the laboratory. 8. Simple substances consist of atoms, each substance having its own special atom.

Ex. 13. Write the translation of the following text:

Consideration of the masses of the isotopes shows that they are not additive’, the mass of the ordinary hydrogen atom being 1.00813, and that of the neutron being 1.00897.

If the helium atom were made from two hydrogen atoms and two neutrons without change in mass, its mass would be 4.03420, but it is in fact less, only 4.00386.

The loss in mass accompanying the formation of a heavier atom from hydrogen atoms and neutrons is due to the fact that these reactions are strongly exothermic, a very large amount of energy being evolved in the formation of the heavier atoms from hydrogen atoms and neutrons. This amount is so large that the mass of the energy, as given by the Einstein equation E^mc², is significant.

Ex. 14. Render the text:

The ways of obtaining artificial radioactive isotopes are diverse.

The best equipment for obtaining radioactive isotopes in greater quantities is a „cyclotron.

However, its low efficiency and complicated technological operations render it inferior to the nuclear reactor. To obtain radioactive isotopes chemical compounds of different elements are enclosed into a reactor, where they are exposed to inten­sive bombardment with thermal fast neutrons. The method is efficient and relatively cheap, its advantage being that it does not permit to produce all isotopes.

Ex. 15. Read the text and answer the questions that follow:

It is known that the most common reaction is the capture of a neutron by a bombarded nucleus which is attended with emission of gamma quantum and results inlhe formation of a radioactive isotope of the same element.

Bombarding of tellurium oxide with thermal neutrons serves as an example. The isotope tellurium 131 thus produced having a half-life of 24.8 minutes disintegrates into iodine 131 which has a half-life of 8 days.

Another reaction widely used for radioactive isotope pro­duction is where a nucleus captures a thermal neutron emit­ting a proton.

1. What is the most common reaction?

2. What does the reaction result in?

3. /What do you know about the isotope tellurium 131?

Ex. 16/ Read the text and retell It;

Of very great importance for radioisotope production is also use of the fission products of the nuclei of some heavy ele­ments, the most important isotope thus obtained being cesium

137 and strontium 90.

To obtain compounds enriched in stable isotopes a number of physico-chemical separation methods are used, diffusion and thermodiffusion separation, electrolysis, electromagnetic sep­aration being the most important.

Ex. 17. Write the translation of the following text: