Chemical elements were being studied for a long time in the middle of thе 18th century. French scientist Lavoisier laid the foundation of the chemical science, having started the quantitative analysis of the elements. Early in the 19th century English chemist John Dalton tried to establish the atomic theory. By the middle of the 19th century chemical elements had been classified into two general groups: metals and non-metals.
The step forward during this period was the idea of new concept called “valence”, which meant the capacity of atoms to combine with one another. Later, it was found that the properties of chemical elements depend on their atomic weight. So, a Russian scientist D. I. Mendeleyev (1834–1907) could build up a periodic classification of all the then known elements. According to his theory, Mendeleyev predicted the properties of some undiscovered elements for which he left blank spaces. The theory became true and in 1875 such elements as gallium was discovered, taking the place below zinc. Scandium was discovered in 1879, filling the gap below calcium and germanium – in 1886, taking the place near gallium, below zinc. In the memory of the originator of the Periodic Law the 101st element discovered by American scientists in 1951 was named mendeleyevum. Mendeleyev’s Periodic law is regarded to be one of the most recognized and important achievements in science.
D. I. Mendeleyev was not the only Russian scientist dealing with metals. M. V. Lomonosov formulated the first definition of the word “metal” in the following way: “A metal is a bright solid that can be forged”. Besides, the characteristic features of metals are lustre, toughness, workability, electrical and heat conductivity and others. Metals are well processed materials. They can be cast, forged, stamped, extruded, rolled, cut, welded.
It is the presence of iron that divides metals into ferrous and non-ferrous. And it is by this reason that iron may be considered to be the most important element in Periodic Table. The abundance in which iron is founded, its great strength, its remarkable ductility and malleability make it specially suitable for many works where strength with lightness are required. However, in ancient states the use of iron, either cast or wrought, was rather limited, bronze being the favourite metal almost for all purposes. Bronze is known to be the alloy of copper and tin.
Bronze and other non–ferrous metals, such as gold and silver, may be treated in various ways, the chief of which are: casting in mould and treatment by hammering and punching. Along with bronze brass (an alloy of copper and zinc) is widely used because of its cheapness in comparison with bronze. Besides, analyses of the iron of prehistoric weapons showed that they contained a considerable percentage of nickel. And in many specimens of ancient bronze, small quantities of silver, lead and zinc were also found.
It is worth mentioning that both ferrous and non-ferrous metals are widely used in a great variety of works and non-ferrous materials are predominant in works of art. Many metals of Periodic Table can interact with each other and develop quite new materials and alloys. For example, aluminium oxide which is also referred to as corundum, sapphire, ruby or aloxite are mentioned in the mining, ceramic and materials science. Rubies are given their characteristic deep red colour and laser qualities by adding such metallic element as chromium. Sapphires come in different colours given by impurities of iron and titanium. Aluminium oxide is widely used in the fa
brication of superconducting devices, particularly single electron transistors and superconducting quantum interference devices (SQUID).
Such metals as boron and nitrogen form boron nitride known as Borazon. The latter is a crystal created by heating equal quantities of boron and nitrogen at temperatures greater than 18000C (3300 F) at 7 GPa (1 million lbf/in2). Borazon replaced aluminium oxide for grinding hardened steels due to its far superior abrasive properties. Other uses include jewellery designing, glass cutting and laceration of diamonds.
Exercise 3. Complete the sentences:
1. Chemist who established the atomic theory was…
2. There are two general groups of metals:…
3. The capacity of atoms to combine with one another is called…
4. For undiscovered elements Mendeleyev left…
5. The 101st element was named in the memory of …
6. The most important element in Periodic Table is…
7. In ancient works of art the most widely spread metal (alloy) was…
8. Aluminium oxide is widely used in …
9. Borazon replaced aluminium oxide due to …
Exercise 4. Insert the proper words into the sentences:
1. Chemists found a new (понятие) called (валентность).
2. (Свойства) of chemical elements (зависеть от) their (атомный вес).
3. According to Mendeleyev’s theory it is possible (предсказать) the properties of elements.
4. Lomonosov gave the first (определение) of metal.
5. Iron owing to its (эластичность) and (ковкость) is widely used metal.
6. Bronze is (сплав) of copper and tin.
7. In many (образец) of ancient bronze some (примесь) of other metals have been found.
8. (Цветные металлы) are mainly used in works of art.
9. Aluminium adds (сверхпроводимость) to its alloys.
10. Borazon is used for (шлифовать) hardened steels.
Exercise 5. Find in the text the sentences that correspond to the following statements:
1. In the middle of 19th century classification of chemical elements appeared.
2. Due to the quantitative analysis of chemical elements new concept emerged.
3. Mendeleyev’s theory gave the opportunity to foresee the properties of elements.
4. Gradually several elements which filled the gaps in the Table were discovered.
5. Metals can be processed by various operations.
6. Owing to its qualities iron is the most important element in the Table.
7. Earlier the most popular metal was bronze.
8. Ancient weapons contained impurities of several non-ferrous metals.
9. Interaction of metals can result in other materials and alloys.
10. Such metal as boron possesses high strength and is used for grinding hardened steels and cutting diamonds.
Exercise 6. Translate into English:
1. Количественный анализ элементов, придуманный французским ученым Лавуазье, стал основой химической науки.
2. Понятие валентности означает способность атомов соединяться друг с другом.
3. Атомная теория Джона Дальтона была подтверждена русским ученым Менделеевым.
4. Свойства химических элементов зависят от их атомного веса.
5. Предсказанные свойства неоткрытых элементов подтвердились.
6. В результате новые элементы заполнили пропуски в таблице.
7. Один из вновь открытых элементов был назван в честь создателя периодической таблицы.
8. Одно из определений слова «металл» было дано Ломоносовым.
9. Основными свойствами металлов являются: прочность, эластичность, ковкость, электро- и теплопроводность.
10. Металлы могут быть обработаны ковкой, штамповкой, прокаткой, резанием, сваркой и другими способами.
11. Металлы делятся на цветные и черные и могут взаимодействовать друг с другом, образуя сплавы.
Exercise 7. Give the summary of the text, using key vocabulary and tell about:
a) scientists engaged in chemical science;
b) atomic theory;
c) discovery of unknown elements;
d) characteristic features of metals;
e) the ways of processing metals;
f) ability of metals to interact with each other.
Checklist for Section I:
1. How is Absolute Participle Construction translated into Russian?
2. What are the suffixes of abstract nouns?
3. What were the preconditions of appearing Periodic Table?
4. What are the main properties of metals?
5. How can metals be processed?
Дата добавления: 2015-07-07; просмотров: 216 | Нарушение авторских прав
|<== предыдущая страница|||||следующая страница ==>|
|Section I. Metals in Periodic Table|||||Types of Metals|