|
Hydrogen
Hydrogen is the lightest chemical element. Its mass is die unit of measurement for the masses of other elements.
Atomic weight, or mass, was long considered the most important property of an clement. By weighing the amounts of individual elements making up a chemical compound and calculating the weights of these ratios to the weight of hydrogen which will combinc with the same elements, it is found that the atomic weights of the other elements are almost, but not quite, whole numbers.
During the nineteenth century a committee of chemists was chosen to decide upon a standard of accuracy for atomic weights. The committee set the atomic weight of oxygen at 16.000 in order to make the atomic weights of other elements come out closer to whole numbers. That change of standards gave hydrogen the weight of 1.008.
Hydrogen was first obtained in 1766 by Sir Henry Cavendish in London. He found that he could get the gas by dissolving zinc, iron or tin in diluted vitriolic acid (H2SO4) or spirit of salt (HCl). He discovered that a mixture of hydrogen and common air explodes with a long noise, and he was impressed with the lightness of the gas. He named the gas “inflammable air”, the name “hydrogen” (water-former) was given by Lavoisier.
Hydrogen exists in three isotopic forms, known as hydrogen (or protium), deuterium and tritium. Tritium is radioactive, with a short half-life. Deuterium is stable, and occurs in a small amount with ordinary hydrogen. Its compound (D2O ) is known as heavy water. Slight differences between the properties of ordinary water and heavy water allow their separation, notably by electrolysis, in which ordinary water is decomposed and heavy water becomes concentrated in the water left in the apparatus.
The nuclear structure of ordinary hydrogen consists of one proton, the unit of matter. This is the same as a hydrogen ion. An electron as the sole planet in this system completes the structure of hydrogen atom.
The difference between ordinary hydrogen and heavy hydrogen (deuterium) lies in the fact that deuterium has a neutron in the nucleus in addition to the proton. Addition of the neutron adds weight but does not change the chemical characteristics. This is in accordance with a general rule covering structures of elements.
Tritium has a nuclcus consisting of one proton and two neutrons. Hydrogen is given oiTby some natural gas wells, but it cscapcs into the upper air. It is not found uncombincd on the earth. It is recognized in the stars by its spectrum lines in the light that We receive from them.
In combination with oxygen, in the form of water, and with carbon, in the many organic compounds, hydrogen is one of the most abundant elements on the earth.
Hydrogen combines with other elements and forms different kinds of compounds, some of which ionize in solution, others which are joined with covalent bonds, yielding organic types of compounds.
Although formerly it used to be classed with the alkali metals of Group 1 in the periodic table, hydrogen acts as a negative part of the molecule when it is in combination with those metals. It forms hydrides which are in general colourless crystals. Similar compounds are formed with calcium and barium of Group II. The hydrides decompose in water, releasing hydrogen. This properly has been used as a convenient way to store hydrogen.
Hydrogen is usually obtained by action of sulphuric acid (H2SO4) on zinc. The metal replaces the hydrogen, which bubbles оПГ a gas. Electrolysis of water also liberates hydrogen at the cathodc, while oxygen comes off at the anode.
Words and Word-Combinations to Be Memorized
in accordance with, act, action, alkali, anode, apparatus, barium, bond, carbon, choose, come out, combine, concentrate, consider, covalent, decompose, difference, dissolve, electrolysis, electron, explode, form, general, give off, half-life, hydride, hydrogen, ion, ionize, line, measurement, molecule, negative nucleus, in older to, ordinary, radioactive, separation, spectrum, stable, standard, sulphuric, tin, unit, whole, zinc
Ex. 6. Give the Uzbek equivalents for the following:
unit of measurement, make up a compound, whole numbers, a committee of chemists, a standard of accuracy, in order to, weigh, dissolve, zinc, iron, a diluted acid, common air, the lightness of the gas, hydrogen, an isotopic form, radioactive, a short half-life, stable, a small amount, ordinary, heavy water, slight difference, electrolysis, apparatus, consist of, the unit of matter, an ion, an electron, complete the structure, the difference lies in the fact, in addition to the proton, change the chemical characteristics, be in accordance with, a rule, a neutron, a proton, to give off, escape into the upper air, in the stars, spectrum lines, different kinds of compounds, in solution, similar compounds, at the cathodc, at the anode
Ex. 7. Give the English equivalents for the following:
gazni topish, eritish, sulfat kislotani suyultirish, oddiy havo, engil gaz, izotopik shakl, radioaktiv, qisqa umr, kimyoviy birikma, og'ir suv uchun eng engil kimyoviy element, o'lchov birligi, eng muhim xususiyat, butun son. , ozgina farqlar, elektroliz, umumiy qoidaga muvofiq, spektr chiziqlari, suv shaklida, boshqa elementlar, turli xil birikmalar bilan birlashadi, eritmada ionlanadi, ishqorli metallar, gidrid, parchalanadi suvda, katodda, anodda
Ex. 8. Fill in the blanks with prepositions where necessary.
Do'stlaringiz bilan baham: |
