English for chemists

Lesson 20
ГРАММАТИКА: Инфинитив и инфинитивный оборот в функции допол­ нения.
Section I
Ex. I. Practise your pronunciation.
a) covalent [kao'veibnt], distribute [dis'tnbjot], electron [f Icktron], ethyl
['cOilj, [*i:0ail] (chem.), dimethyl [dat'meOil]. [-mi:6ail] (chem.), ether [Ч:0э].

136

alcohol ['x’lkahnlj, hydroxyl [hai'droksil], California [,ka:b'fo:nio], through [Oru:J, clcctronic [ilek'tromk]
b) Jhc^clcc'troniCy'structurCyOfNmolcculcs, the^’number^of^'valcncc electrons, un'sharcd^c’lcctronXpairs, in^'such^aSway, in^itsw'ouicrw\shcll, forw'othcr\molecules, forv'ovcrva^ 'hundrcd\years, atjheJjc'ginning^of^thc Ncentury

c) It is the coValent/bond | that is .represented by a 'dash in the 'valcnce-bond\formulas.

Ex. 2. Pay attention to the structure of the following words. Translate them into Russian.

1. 
   hydrogen, hydroxyl, hydrate, hydride, hydrocarbon, hydrolysis, hydrolyze, hydroxide, hydrochloric acid
   
2. 
   a chcmical, a proposal, a general, a crystal, a credential, a liberal, a criminal
   

3. 
   sulphide, halide, fluoride, hydride, bromide, oxide, sclcnidc, nitride, iodide, chloride
   

Ex. 3. Define the meanings of the word way in the following scntcnccs:

1. In what way is hydrogen produced? 2. The tcachcr didn’t like the way the student was handling the instrument. 3. The situation is rather difficult, I don’t see any way out. 4. The compound obtained in this way is usually pure enough. 5. In some way or other, the work must be finished today. 6. It is a long way from here to his home. 7. On his way home he met N. 8. By the н’л>\ what is the symbol of manganese? 9. The investigation that is under way in their laboratory is of particular interest.
Ex. 4. Find the predicate, the subjcct and the object in the following sentences:

1. 
   The chcmical properties show ethyl alcohol to contain one hydrogen
   

• 
  atom attached to an oxygen atom. 2. Before 1900 many chcmists believed water to be the only solvent in which typical ionic reactions could be cairicd out. 3. Dalton assumed atoms to be indivisible particles of the elementary substancc.
  

Text 20 A

The Structure of Covalent Compounds
The clcctronic structure of molcculcs ofcovalcnt compounds involving the principal groups of the periodic table can usually be written by counting the number of valcncc electrons in the molecule and then distributing the valcncc electrons as unshared electron pairs and shared electron pairs in such a way that each atom achieves an argonic structure.
For many molcculcs the covalcncc of cach atom is equal to the number of unpaired clcctrons in its outer shell, and is, thus, simply related to the position of the clement in the periodic table. For other molcculcs and ions the covalcncc of the atoms is less simply related to the periodic tabic.

137

It is often ncccssary to have some experimental information about the way in which the atoms arc bonded together. Thus, there arc two compounds with the composition C;H60: ethyl alcohol and dimethyl ether. The chcmical properties of these two substanccs show one of them, ethyl alcohol, to contain one hydrogen atom attached to an oxygen atom, whereas dimethyl ether doesn’t contain such a hydroxyl group.
The atoms of most molcculcs arc held tightly together by a very important sort of bond, the sharcd-clcctron-pair bond or the covalcnt bond. This bond is so important, so nearly universally present in substancc that Professor Gilbert Newton Lewis of the University of California (1876— 1946), who discovered its electronic structure, callcd it the chcmical bond.
It is the covalcnt bond that is represented by a dash in the valence-bond formulas, such as
Cl
I

Br—Br and Cl — С — Cl

I

Cl
that have been written by chcmists for over a hundred years.

Modem chemistiy has been greatly simplified through the development of the theory of the covalcnt bond. It is now easier to understand and to remember chcmical facts, by connecting them with our knowledge of the nature of the chcmical bond and the electronic structure of molcculcs, than was possible at the beginning of the ccntury.
Words and Word-Combinations to Be Memorized
achieve, argon, such a, connect, ether, ethyl, experimental, greatly, infoimation, nearly, professor, simplify, sort, universally, university, covalent, in such a way, in this way
Ex. 5. Give the Russian equivalents for the following:
the principal groups of the periodic tabic, count the number of valcncc electrons, distribute the electrons, unshared clcctron pairs, in the outer shell, be related to, it is often ncccssary to, be bonded together, attach one atom to another, a hydroxyl group, be held together, represent the bond by a dash, over a hundred years, it is now easier to understand, the theory of the covalcnt bond
Ex. 6. Give the English equivalents for the following:
ковалентное соединение, поделенная электронная пара, таким образом, быть равным чему-л., положение элемента в периодической таблице, этиловый спирт, присоединить к, ковалентная связь, Кали­ форнийский университет, Санкт-Пстсрбургскнй университет, соврс-

138

мснная химия, упростить что-л., запомнить факты, природа хими­ ческой связи, электронная структура молекулы, быть возможным, в на­ чале столетня
Ex. 7. Fill in the blanks with prepositions where ncccssary.

1....	many molcculcs the covalcncc ...				cach ...	atom is equal...	the
number...		unpaired electrons ...		its outer level. 2. There are some other
molcculcs		... which the covalcncc... the atoms is not dircctly related...
the periodic table. 3			ethyl alcohol one hydrogen atom is attached...					an
oxygen atom. 4. Dimethyl ether docs not contain ...						a hydroxyl group.

5. 
   The atoms ... most molcculcs arc held together ... a covalcnt bond.
   
6. 
   Modem chcmistry was greatly simplified ... the development... the theory ... the covalcnt bond.
   

Ex. 8. Translate the sentences into Russian, paying attention to different functions of one.

1. There is some difference as regards solubility of gases in liquids, of two gases the one that is more readily liquefied is the more soluble. 2. The transition elements arc the ones that have their inner shells partly filled.

3. 
   Ethyl alcohol contains one hydrogen atom attached to an oxygen atom.
   
4. 
   Now one can understand chcmical phenomena better by connccting chemical facts with the nature of the chcmical bond. 5. Reliable experimental data enable one to draw proper conclusions. 6. This approach is quite similar to the one just described. 7. The procedure is a simple one.
   

8.