3 Part One. The Predicate

The Atomic Theory
In 1805 the English chemist and physicist John Dalton (1766-1844) put forward the hypothesis according to which all substances were stated to consist of small particles o f matter, of several different kinds, corresponding to the different elements. He called these particles atoms, from the Greek word atomos, meaning “indivisible”. This hypothesis gave a simple explanation or picture of previously observed but unsatisfactorily explained relations among the weights of substances taking part in chemical reactions with one another. As it was verified by further work in chemistry and physics, Dalton’s atomic hypothesis became the atomic theory.

The rapid progress of science during the twentieth century is well illustrated by the increase in our knowledge about atoms. In a popular textbook of chemistry written in the early years of the twentieth century, atoms were defined to be the “imaginary units” of which bodies are ''aggregates. The article in “Atom” in the 11th edition of the Encyclopaedia Britannica,published in 1910, ends with the words “The atomic theory has been of priceless value to chemists, but it has more than once happened in the history of science that a hypothesis, after having been useful in the discovery and the coordination of knowledge, has been abandoned and replaced by one more in harmony with later discoveries.

Some distinguished chemists thought that this fate may be awaiting the atomic theory... But modem discoveries in radioactivity are in favour of the existence of the atom, although they lead to the belief that the atom is likely to be not so eternal and unchangeable a thing as Dalton and his predecessors had imagined”.

Only half a ccntuiy later, scientists had precise knowledge of the struc­ture and properties of atoms and molecules. Atoms and molecules can no longer be considered “imaginary”.

Words and Word-Combinations to Be Memorized

article, current, define, distinguish, explanation, in favour of, illustrate, increase, no longer, more than once, physicist, physics, popular, precise, previously, price, priceless, progress, put forward, radioactivity, rapid, replace, satisfactory, useful, be of value

Ex. 5. Give the Uzbek equivalents for the following:

put forward a hypothesis, according to the atomic theory, give an explanation, previously observed relations, by further work, rapid progress, during the current century, be illustrated by smth., imaginary units, be o f value, replace a hypothesis by a theory, a distinguished chemist, discoveries in radioactivity, be in favour of smth., imagine, have precise knowledge, no longer

Ex. 6. Give the English equivalents for the following:

g'oyani ilgari surish, nazariyaga ko'ra, oddiy tushuntirish berish, haqiqatni tushuntirish, reaktsiyada ishtirok etish, bir-birlari bilan mashhur kitob, uchinchi nashr, maqolani nashr qilish, bitta g'oyani boshqasi bilan almashtirish, taniqli olim, gipoteza foydasiga olib borilgan argumentlar, yarim yildan so'ng, endi bo'lmaydi. ko'rib chiqilgan, radioaktivlik darajasi bir necha bor, ilgari noma'lum bo'lgan, tezkor rivojlanish

Ex. 7. Fill in the blanks with prepositions where necessary.

1 . Dalton's theory was put... 1805.2. The hypothesis could not explain ... relations... the weights... substances taking part... chemical reactions.3. The atomic theory is ... priceless value ... chemists. 4. Modem discoveries... radioactivity a rc ... the existence... the atom. 5. Half... a century later the atomic structure became clear. 6. The atomic theory is useful... the coordination ... knowledge. 7. Dalton’s atomic hypothesis was verified ... further work ... chemistry and physics.

Ex. 8. Translate the sentences into Uzbek paying attention to different functions offor.

1. The atomic theory was of great value fo r further development of science. 2. Dalton’s hypothesis became the atomic theory, fo r it was verified by later discoveries. 3. For this reason the hypothesis'was replaced by another one. 4. This technique is recommended to be used, for it is very accurate. 5. Argon and other gases of this group are called inert, fo r they are chemically inactive. 6 . The theory hasn’t been recognized fo r almost a century.

Ex. 9. Translate the sentences into Uzbek.

a) 1. Dalton’s hypothesis was later proved to be true. 2. Fundamental particles are no longer considered to be non-existent. 3. Radioactivity is known to be affected by the presence of other elements which are not radioactive. 4. Air was later found not to be an element. 5. Hydrogen does not appear to react quickly with chlorine in the dark. 6 . Pure liquid HCl does not seem to be conductor of electricity. 7. Under certain conditions an atom of hydrogen may be regarded to be acting as a bond. 8. There appears to be no difficulty in determining the rate of this reaction. 9. There seems to be no evidence in favour of your idea. 10. The phenomenon has never been observed to occur under ordinary conditions. 11. Chlorine is stated to have been discovered in 1774.12. Solid carbon is usually said to exist in three modifications. 13. Mendeleyev is known to have been bom in Tobolsk. 14. The law of conservation of mass is known to have been definitely stated by the great Russian scientist М. V. Lomonosov in 1756. 15. H₂SO₄ does not appear to have been known to the ancient world.

b) 1. The symbol H₂SO₄ is interpreted as representing one molecule of sulphuric acid. 2. Acids are usually thought of as being liquids. 3. According to the atomic theory, a molecule is considered as being composed of atoms.4. The periodic classification should be mentioned as having been the principal discovery of the 19th century. 5. A nucleus is now regarded as being composed of fundamental particles. 6 . All substances may be regarded as soluble in water. 7. Atoms are no longer considered “imaginary”. 8. The valency of carbon is usually thought of as four. 9. Water is known as composed o f two elements: hydrogen and oxygen.10. Substances are usually defined as having a definite composition.
Ex. 10. Translate the sentences into English.

1. D. Dalton kimyogar va fizik edi. 2. U 1766 yildan 1844 yilgacha Angliyada yashagan. 3. U eng avvalo o'zining atomistik nazariyasi bilan tanilgan. 4. Dalton 1805 yilda elementlarning tuzilishi haqidagi nazariyasini ilgari surdi. 5. Ushbu nazariya keyingi tadqiqotlar bilan tasdiqlangan. 6. Keyinchalik zamonaviy tadqiqotlar asosida ishlab chiqilgan. 7. Zamonaviy fan atomlar va molekulalarning tuzilishi va xususiyatlari to'g'risida aniq ma'lumotga ega. 8. Endi boshqa hech kim atomlarning tuzilishi va tarkibi noma'lum deb da'vo qila olmaydi.

Ex. 11. Answer the following questions:

1. When was Dalton’s atomic hypothesis put forward? 2. What was the main idea of this hypothesis? 3. In what way was the hypothesis verified? 4. What does sometimes happen to a hypothesis in the course of history? S. Was Dalton’s hypothesis forgotten later? 6. What do modem scientists think about Dalton’s theory?