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The story of how D. I. Mendeleyev established the Periodic System of Elements has long been a matter of great interest to research workers.

When Mendeleyev began to teach at St. Petersburg University, chemistry was still far from being the well-ordered and harmonious branch of science that we know today.

The great majority of scientists were firmly convinced that atoms of different elements were in no way connected with each other, and that they were quite independent particles of nature. Only a few advanced scientists realized that there must be a general system of laws which regulates the behaviour of atoms of each and every element. However, the few attempts made by Beguyer de Chancourtois, Newlands, Lother Meyer and others to find a system of laws controlling the behaviour of atoms were unsuccessful and exercised no influence on Mendeleyev, the future founder of the Periodic System of Elements.

"Mendeleyev was a man who could not bear any kind of disorder and chaos," writes Academician A. A. Boikov. "This is why at the beginning of his course in chemistry at St. Petersburg University, where he had been appointed to the department of chemistry, D. I. had to establish order in the chemical elements."

By comparison of chemical properties of different elements researchers had long ago discovered that elements could be placed in several groups according to similarity in their properties.

Mendeleyev applied in his system the principles that he developed and included in his table the listing of the elements according to increasing weights.

Because he had the insight to see that many elements had not yet been discovered, he left open spaces in the Periodic Table. For example, he predicted that an unknown element with atomic weight of 44 would be found for the space following calcium. And in 1879 the Swedish chemist Lars Fredric Nilson discovered scandium.

Mendeleyev's table developed into the modern Periodic Table, one of the most important tools in chemistry. The vertical columns of the modern Periodic Table are called groups and the horizontal rows are called periods. The atomic number of an element is the number of protons in the nucleus of the atom of that element. The modern Periodic Table not only clearly organizes all the elements, it lucidly illustrates that they form "families" in rational groups, based on their characteristics.

TEXT STUDY

1. Ще раз продивіться текст та знайдіть речення, в яких автор описує наступні факти:

1. Mendeleyev could foresee the existence of new elements because he was very gifted.

2. Scientists of Mendeleyev's time didn't believe that elements are connected with each other.

3. Mendeleyev's character made him order the elements.

4. Mendeleyev's work on the Periodic Table and the Periodic Law has long interested scientists.

5. There were some scientists' attempts to find a system to order the elements but they failed.

6. Thanks to Mendeleyev modern chemistry uses the clearly developed Periodic System as the main instrument.

2. Прочитайте текст за допомогою словника та дайте відповіді на наступні запитання:

1. Where did Mendeleyev start ordering the elements?

a) at school;

b) at St. Petersburg University;

c) abroad.

2. Why did Mendeleyev turn to ordering the elements? Because:

a) other scientists' attempts failed;

b) he had talent;

c) he didn't like disorder.

3. What did the researchers try to do to find some order of the elements?

a) they compared different properties;

b) they read scientific literature;

c) they denied the earlier attempts of the scientists.

4. How did Mendeleyev list the elements?

a) according to their names;

b) according to their atomic weights;

c) according to their chemical symbols.

5. What did scientists of Mendeleyev's time think about atoms of different elements?

a) they were independent particles of nature;

b) they were closely connected;

c) they belonged to a well-ordered system.

3. Знайдіть українські еквіваленти наступним словам, словосполукам та термінам з тексту С:

1. research worker            10. to exercise              18. applied

2. well-ordered                 11. to influence             19. increasing

3. majority                             12. could not bear         20. insight

4. firmly                                 13. had been appointed  21. for example

5. were convinced                                                  22. weight

6. particles                             14. disorder                  23. tools

7. advanced                            15. comparison            24. nucleus

8. realized                     16. according to            25. lucidly

9. unsuccessful                 17. similarity                26. density

4. Поєднайте синоніми з вправи 3 та вправи 4:

a) to affect                    i) for instance               r) properly organized

b) investigator              j) centre                            s) in agreement with

c) were sure              k) very small bits         t) thickness

d) unlucky                    1) understood               u) used

e) resolutely           m) to exert                        v) disliked very much

f) progressive               n) chaos                        w) intuitive cognition

g) had been given          o) likeness               x) heaviness

a position                 p) making greater          y) clearly

h) instruments               q) collation                   z) a greater number

 

TEXT D

Уважно прочитайте наступний текст та доберіть назву, що найбільш підходе:

1. History of Scientific Discoveries.

2. Mendeleyev's Contribution to Chemistry.

3. Elements of the Periodic Table.

4. The Periodic System of Elements.

In spite of the importance of the contributions that had been made earlier, the greatest portion of credit for the development of the Periodic System must undoubtedly go to the Russian scientist, D. I. Mendeleyev. The understanding that the properties of the elements can be represented as periodic functions of their atomic weights made possible classification that has suffered few significant changes in the subsequent years. In March of 1869 D. I. Mendeleyev published his first description of the Periodic System in which he gave the arrangement of the elements in terms of their increasing atomic weights. He fully realized the importance of this periodicity. In his first article D. I. Mendeleyev pointed out the similarities of a number of properties of certain elements and changed the order of atomic weights where necessary in order to have the group similarity. D. I. Mendeleyev left vacant positions in his table for yet undiscovered elements and expressed the opinion that the chemical and physical properties of the elements would be discovered, as he predicted, from their positions in the table. In the summer of 1871 D. I. Mendeleyev published a more comprehensive work and called it the Periodic Law. At this time he presented the more familiar form of the Periodic Table and although it differs somewhat from the one we use today, it is in general the same. In his publication of 1871 D. I. Mendeleyev used the periodic character to predict the properties of the elements which would be later described as those of scandium, gallium, and germanium. The remarkable agreement of the properties of these elements as they had been described by Mendeleyev and those that were observed later is without doubt a complete justification of D. I. Mendeleyev's faith in his Periodic Law. In December 1945 Glenn Seaberg made his first publication of a Periodic Table which described a new actinide series beginning with actinium. He said that American scientists were proud and happy to honour the name of D. I. Mendeleyev by calling element 101 "mendelevium".

TEXT STUDY

1. Поставте пункти плану до тексту D в правильному порядку:

Plan:

1. Advent of the Periodic Law.

2. Discovery of "Mendelevium".

3. Similarities of Elements' Properties.

4. The Inventor of the Periodic System of Elements.