3 Part One. The Predicate

Molecules
To the modem chemist, the atom is the smallest particle of an element that can enter into a chemical reaction. Thus, cach element has atoms that are peculiar to itself and different from those of cach of the other elements.

Chemical reactions occur when atoms of different kinds unite to form groups in which they bear definite relationships to cach other or when these groups undergo disruption or rearrangement. Chemical unions are of two general types.

In one type of union, atoms become bonded together to form definite aggregates that exist as independent, electrically neutral particles and are known as molecules (Latin “little mass”). Some elements have atoms that unite with others o f their own kind to form molecules. These are known as elemental molecules and are exemplified by the chlorine molecule which is made up of two chlorine atoms. Compound molecules are composed of two or more kinds o f atoms and are exemplified by the water molecule, which contains two atoms of hydrogen and one of oxygen.

To give a short definition of a molecule is not to give a more or less full account of properties.

Molecules are regarded as the smallest particles or elementary substances that can have independent existence. They account for the chemical properties and at least some of the physical properties of the substance they constitute. A single molecule does not exhibit in full the physical properties commonly associated with its particular variety of matter. These properties arise both within the molecule itself and within the aggregates of like molecules that constitute a sample of the given substance. The density of water depends not only on the mass and volume of indivilual molecules but also on the manner in which the molecules are packed together. Since the chemist works with the aggregates, their properties are of great practical importance.

A molecule of a compound contains, of necessity, at least two di ffcrent atoms. An element molecule may contain only one atom, or it may contain two or more. Helium has monoatomic molecules; chlorine and hydrogen cach exist as diatomic molecules; and sulphur molecules contain eight atoms. During reactions the atoms of elemental molecules usually are separated and individually redistributed in new combinations.

Words and Word-Combinations to Be Memorized

arise, be made up of, be of importance, both... and, commonly, constitute, definition, density, depend (on), distribute, cach other, helium, independent, at least, manner, more, neutral, pack, particular, rearrangement, relationship, sample, those, type, union, within

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

enter into a chemical reaction, be different from cach other, occur, definite relationships, undergo rearrangement, chemical unions, become bonded together, form definite aggregates, be exemplified by, give a full account of, account for chemical properties, a single molecule, exhibit a property, arise within the molecule itself, density, depend on the mass, pack the molecules together, be o f great practical importance, contain two or more atoms, exist as diatomic molecules

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

Kimyoviy reaktsiyaga kiradigan har bir element elektrdan neytral, xlor molekulasi murakkab molekuladan, aralash molekuladan iborat bo'lib, bir necha turdagi atomlardan iborat, suv molekulasi, qisqacha ta'rifi, ko'proq yoki ko'proq, kamida ba'zi xususiyatlari bitta molekula, molekulaning o'zida ma'lum bir moddaning namunasi, moddaning zichligi (o'ziga xos tortishish kuchi) amaliy ahamiyatga ega, monatomik molekula

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

1. The smallest particle of an clement that can enter ... a chemical reaction is an atom. 2. The lecture has already begun, don’t enter ... the classroom, please. 3. Elements differ... cach other. 4. Atoms ... different kinds can unite and form a molecule ... a compound. 5. Elemental molecules are composed ... the atoms ... the same kind. 6. Chlorine molecule is made... two chlorine atoms. 7. This definition does not give a full account... the properties of a molecule. 8. The density... a substance can be easily calculated, it depends ... its mass and volume.

Ex. 8. Translate the sentences into Uzbek, paying attention to different functions of since.

1. We call the atomic hypothesis a theory, sinceit has been verified by further discoveries. 2. Bohr’s atomic theory has been known since1913. 3. Chemistry has changcd greatly since 1869 when the periodic law was published. 4. The periodic system has long since served as the greatest contribution to science. 5. Sincethe combustion of many non- metals yielded products which rcaetcd with water and gave acidic solutions, Lavoisier named the ncwly-discovercd gas oxygen (“acid former"). 6. Ever sinceLavoisier in 1792 demonstrated that diamond and graphite are allotropic forms of carbon, man has been interested in converting carbon into diamond. 7. They left St. Petersburg in 1996, they haven’t been there sincethen.

Ex. 9. Translate the sentences into Uzbek.

1. To analyse a substance means to define its components. 2. To have a laboratory practice work is very useful for students of chemistry.3. To know the atomic structure is to understand this phenomenon.4. To give a short definition o f a molecule is not so very easy. 5. For uranium minerals to be used in industry is not a usual thing. 6. For atoms to have the same chemical properties is to be the atoms of one element. 7. To make accurate measurements requires great care. 8. To start a reaction is one thing, but to keep it going on is another.

9. For molecules to have the same composition implies the existence o f the same structure. 10. To think about ordinary conditions of a reaction means to think about room temperature and 1-atm pressure. 11. To speak about the properties o f galogens is first o f all to mention their extraordinary activity. 12. For compounds to be bonded by a covalent bond implies having one or more shared electron pairs. 13. To compare the size o f molecules is rather difficult. 14. To imagine a molecule of water means to imagine a certain combination o f hydrogen and oxygen atoms. 15. To obtain a spectrum is to pass a beam of white light through a spectrograph. 16. To say that the density o f a substance depends only on its mass and volume is to lose sight o f the manner in which the molecules are packed together.
Ex. 10. Translate the sentences into English.

1. Har bir elementning atomlari boshqa elementlarning atomlaridan farq qiladi. 2. Kimyoviy reaktsiya atomlar bir-biri bilan o'zaro ta'sirlashganda va yangi birikmalar hosil bo'lganda sodir bo'ladi. 3. Molekulalar elektr neytral ekanligi ma'lum. 4. Aralashmalarning molekulalari ikki yoki undan ortiq turdagi atomlardan iborat. 5. Molekulani aniqlash uning tarkibi va xossalari haqida gapirishga yordam beradi. 6. Birlashmalarning fizik xususiyatlari bir xil bo'lishi ularning kimyoviy xossalari ham bir xil ekanligini anglatmaydi. 7. Elementning molekulasi bitta, ikki yoki undan ko'p o'xshash atomlardan iborat bo'lishi mumkin.

Ex. 11. Answer the following questions:

1. What is a chemical reaction? 2. What types of chemical unions do you know? 3. What is an elemental molecule? 4. What is a compound molecule? 5. What determines the properties o f a molecule? 6. What composition an elemental molecule may have? 7. What is the difference between an atom and an elemental molecule?