X. Match the words in column a with their definitions in column b. Define the part of speech the words in column a belong to.

A	B
1) determine	a) totally
2) increase	b) to find something out
3) property	c) to say in advance that something will happen
4) predict	d) a natural quality of something
5) considerable	e) the usefulness or importance of something
6) completely	f) a rise in amount, number, or degree
7) value	g) fairly large

XI. Look through the text d. I. Mendeleyev and discuss the main points of Mendeleyev’s biography.

2. When was D. I. Mendeleyev born?

3. Where was D. I. Mendeleyev born?

4. What Institute did he enter?

5. Where did Mendeleyev work after the graduation from the Institute?

6. What was Mendeleyev awarded the Doctor of Science degree for?

7. What was Mendeleyev’s greatest discovery?

8. What is the main idea of the Periodic System?

9. What kind of difficulties had Mendeleyev to overcome arranging the elements in the table?

10. What problems was Mendeleyev interested in?

11. What kind of changes did the Periodic Table of Mendeleyev cause?

XII. Read the sentences, translate them from Russian into English.

1. Работая по теме своего исследования, Менделеев проанализировал огромное количество литературы.

2. Открытия Менделеева имели большую как теоретическую, так и практическую значимость.

3. Начиная работу над «Основами химии», Менделеев провел тысячи опытов, сделал множество вычислений.

4. Таблица элементов состояла из вертикальных групп и горизонтальных периодов и была результатом колоссальной работы ученого.

5. Система классификации, в которой элементы расположены в порядке увеличения атомного веса, была предложена Менделеевым.

6. Ученому было трудно распределить все имеющиеся элементы в таблице, поскольку многие элементы были неизвестны, а атомный вес девяти элементов был определен неправильно.

7. Главная идея периодической системы Менделеева состоит в периодическом повторении свойств элементов по мере увеличения атомной массы.

8. Ученый смог предсказать наличие нескольких неизвестных элементов, а также их свойства.

XIII. Retell the text D. I. Mendeleyev according to the following plan.

1. Mendeleyev’s studies.

2. Mendeleyev’s academic position at St. Petersburg University.

3. Mendeleyev’s research work.

4. The greatest discovery of Mendeleyev.

5. Mendeleyev’s contribution to science.

XIV. 1) Look through this text and find the answer to the question “What important scientific discovery did the Periodic Law help to open up?”

2) Read carefully the text where you can get additional information about Mendeleyev’s Periodic Table.

3) Make up a plan of the text. Prepare a summary according to each point of the plan.

THE PERIODIC TABLE OF D. I. MENDELEYEV

The Periodic Law discovered hundred years ago plays a great part in the development of modern chemistry and physics.

There are certain natural groupings among the chemical elements in which every element is closely related to¹ the other elements in its group. In order to² understand better these groupings, chemists have tried to fit the elements into a single plan.

One of the earlier attempts to fit the relationships³ among the elements into a single law was made by John Newlands in England; he suggested the Law of Octaves.

This concept of the periodic repetition of properties was further developed by a Russian chemist Dmitri Mendeleyev. He created a Periodic Table in which he arranged the elements according to their atomic weights and corresponding chemical properties.

D. I. Mendeleyev listed the elements known at that time (1869) in the order of their atomic weights from the lightest to the heaviest. The elements were arranged in a table of eight columns. Elements having similar properties appeared in the same columns or groups in the table. Mendeleyev even predicted that there were undiscovered elements and left empty spaces⁴ in this table for the new discoveries. At the time when D. I. Mendeleyev published his Table only 63 elements were known. Now 114 elements are known.

There are many ways the Periodic Table can be used. The table shows the atomic number; the atomic weight of an element is also indicated there. Besides, the orbital arrangement of electrons⁵ is shown for each of the elements. The common oxidation states are given: for the most elements these numbers are the same as valence numbers.

The table enables to recognize⁶ families of elements. For example, copper (29), silver (47) and gold (79) will all be found in the same column. They have similar properties and are considered as a chemical family.

The table can be used to predict the properties of the elements. The fact that the Periodic Table can help in predicting properties of elements caused the discovery of missing elements⁷.

The importance of D. I. Mendeleyev’s discovery is not limited to chemistry alone. The Periodic Law opened up the way to the discovery of the atom structure and its nucleus.

In more than hundred years of its existence the Periodic Law did not lose its significance. The Periodic Law became the property⁸ of all nations, like the works of Newton, Lomonosov, Einstein and other great scientists.

Vocabulary notes:

¹ is closely related to – тесно связан с

² in order to – чтобы

³ to fit the relationships – установить связь

⁴ empty space – пустое пространство

⁵ the orbital arrangement of electrons – расположение электронов на орбите

⁶ enables to recognize – позволяет распознать

⁷ missing elements – недостающие элементы

⁸ property – достояние