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Юриспунденкция

THE PERIODIC LAW

In the eighteenth century many chemists began to identify elements and study their pro­perties. A lot of attempts were made to classify them. The most outstanding classification was made by the Russian chemist Dmitry Mendeleev, who published his Periodic Table of Elements in 1869. Mendeleev noticed that if he arranged the elements in order of increasing atomic weight, definite chemical properties repeated themselves periodically. His table of the known elements was constructed with seven elements in each of the first two rows and seventeen elements in each of the next two rows. But there were several blank spots in his table of those elements, which had not been discovered at that time. Mendeleev predicted their existence basing on the observation of periodicity. He even called them ekaboron, ekaaluminum and ekasilicon. Finally, the discovery of gallium, scandium and germanium were made. Mendeleev's table revealed the fact that properties of the elements are periodic function of their atomic masses. This statement was called the Periodic Law.

Now the Periodic Law reads as follows: the physical and chemical properties of the elements are periodic functions of their atomic numbers. The elements are arranged in order of increasing atomic numbers. The value of the Periodic Table consists in the fact that chemists can predict the properties of their compounds by grouping the elements into families and knowing the trends within these families.

Text-based exercises

Exercise III. Underline the correct item and translate the sentences:

1. He appeared at the laboratory after an absence/existence of several weeks.

…………………………………………………………………..………………….............

2. The number of visitors increased/decreased from 210 to 160 this year.

…………………………………………………………………..………………….............

3. I identified/recognized him as soon as he came in the room.

…………………………………………………………………..………………….............

4. You must learn how to construct/builda logical argument.

…………………………………………………………………..………………….............

5. The books are arranged/organized alphabetically by author.

…………………………………………………………………..………………….............

Exercise IV. Find English equivalents for the following Ukrainian word combinations:

Exercise V. Answer the following questions to check your understanding of the text:

1. When did chemists begin to identify elements and study their properties?

…………………………………………………………………..………………….............

2. When did Mendeleev publish his Periodic Table of Elements?

…………………………………………………………………..………………….............

3. What did Mendeleev notice?

…………………………………………………………………..………………….............

4. How does the Periodic Law read?

…………………………………………………………………..………………….............

5. What is the value of Periodic Table?

…………………………………………………………………..………………….............

Grammar exercises

Exercise VI. Put the English equivalents of the Ukrainian words in brackets and translate the sentences:

1. This makes documenting programs …………….. (більш легким).

…………………………………………………………………..………………….............

2. This is the ………….. (найпростіший) way.

…………………………………………………………………..………………….............

3. We will see ……..….. (більше) about the algorithm later.

…………………………………………………………………..………………….............

4. This way of thinking is (менш природний).

…………………………………………………………………..………………….............

5. The forecast of future demand is made …….….... (більш точно).

…………………………………………………………………..………………….............

6. The independent system is …………….. (найбільш поширеним) type of distributed systems.

…………………………………………………………………..………………….............

7. Presence of contaminations troubled us ...………. (більше за все).

…………………………………………………………………..………………….............

8. We will examine this connection ………..… (більш ретельно) than the previous authors.

…………………………………………………………………..………………….............

Exercise VII. Fill in some, any, few, little, much, many:

1. There is a ………….. petrol in the tank. It will get us to the next town.

2. There weren’t …………… people in town today. It was very quiet.

3. I need ……………. advice.

4. I’m tired. I didn’t get ……………… sleep last night.

5. You can do this without ……………… help.

6. There are a ………….. hotels in this town. You’ll probably find the room to spend the night.

Exercise VIII. Form as many words as you can using the suffixes – teen, – ty, – th. Translate the words:

Speaking task

Exercise IX. Tell the story of the Periodic Law discovery. Follow the chronological order in your narration.

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