Практикалық сабақтарының тақырыптары мен мазмұны Practical assignment №1
UNIT 2. SYMBOLS, FORMULAS AND EQUATIONS
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chemistry (1)
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- VOCABULARY molecule
| UNIT 2. SYMBOLS, FORMULAS AND EQUATIONS
STARTING UP. READING INORGANIC MOLECULES AND COMPOUNDS Simple diatomic molecules of a single element are designated by the symbol for the element with a subscript 2, indicating that it contains 2 atoms. Thus the hydrogen molecule is H2; the nitrogen molecule, N2; and the oxygen molecule, O2. Polyatomic molecules of a single element are designated by the symbol for the element with a numerical subscript corresponding to the number of atoms in the molecule. Examples are the phosphorus molecule, P4, and the sulphur molecule, S8. Diatomic covalent molecules, containing unlike elements are given similar designation. The formula for hydrogen chloride is HCl. The more electropositive element is always designated first in the formula. For polyatomic covalent molecules containing unlike elements, numerical subscriptions are used to designate number of atoms of each element present in the molecule, for example, water, H2O. Again, as in diatomic molecules, more electropositive element is placed first in the formula. VOCABULARY molecule - молекула diatomic - двухатомный single – единичный subscript – подстрочный индекс polyatomic - многоатомный numerical – числовой corresponding - соответствующий sulphur – cepa covalent - ковалентный unlikе – различный similar – подобный hydrogen chloride - хлористый водопровод electropositive - электроположительный PERIODIC LAW One of the cornerstones of modern chemical theory is the Periodic Law. It can be simply stated as follows: The properties of the elements are a periodic function of the nuclear charges of their atoms. In 1869 Mendeleyev arrived at the conclusion that by the arrangement of the elements in order of increasing atomic weight the similarity and periodicity of properties of various, valence groups of the elements were clearly delineated. There were several vacant spaces in Mendeleyev's table which led him to predict the existence of six undiscovered elements, (scandium, gallium, germanium, polonium etc). His confidence in the new classification was clearly expressed in the predictions which he made of the chemical properties of these missing elements. And within fifteen years gallium, scandium and germanium were discovered. Although this table has been modified hundreds of times, it has withstood the onslaught of all new facts. Isotopes, rare gases, atomic numbers, and electron configurations have only strengthened the idea of the periodicity of the properties of the elements. жүктеу/скачать 64,23 Kb. Достарыңызбен бөлісу:
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