Are these statements true or false?

1. Dmitry Mendeleyev was a Russian philosopher.

2. Between 1859 and 1861 he worked on fields of oil in Paris.

3. In 1860, Mendeleyev discovered the concept of critical temperature.

4. The Periodic Law reads: "The properties of the elements are a periodic func­tion of the nuclear charges of their atoms".

5. Element number 25, the radioactive mendelevium, is named after him.

3. Read the text. Work in pairs. Find out whether your partner has got the facts about the periodic table right. Ask him when, why and what questions.

PERIODIC TABLE OF THE LEMENTS

The periodic table of the chemical elements is a tabular method of display­ing the chemical elements. This invention is generally credited to Russian che­mist Dmitry Mendeleyev in 1869. Mendeleyev in­tended the table to illus­trate "periodic" trends in the properties of the ele­ments.

In 1869, Mendeleyev classified 56 elements on the basis of their physical and chemical properties in the increasing order of the atomic masses, in the form of a table. Mendeleyev had observed that properties of the elements orderly recur in a cyclic fashion. He found that the elements with similar properties recur at regular intervals when the elements are arranged in the order of their increasing atomic masses. He concluded that "the physical and chemical properties of the elements are periodic functions of their atomic masses". This came to be known as the law of chemical periodicity and stated: "The properties of the elements are a periodic function of the nuclear charges of their atoms".

Based on this law all the known elements were arranged in the form of a table called the “Periodic Table”. D. I. Mendeleyev arranged all the elements in a table consisting of vertical groups and horizontal periods. In this table all the uncoor­dinated data on the properties of elements and their compounds arc collected and arranged into one well-constructed system. It enables scientists to predict the pos­sibility of discovering new elements and their properties and to correct the errors made in previous definitions of the properties of known elements.

The layout of the table has been refined and extended over time, as new ele­ments have been discovered, and new theoretical models have been developed to explain chemical behavior. The periodic table is now used within the academic discipline of chemistry, providing an extremely useful framework to classify, sys­tematize and compare all of the many different forms of chemical behavior. The table has also found wide application in physics, biology, engineering, and indus­try. The table contains 117 elements as of 27 January 2008 (elements 1—116 and element 118).

4. What new information have you learned from the text? Fill in the grid.

5. Find words in the text that mean the following:

a) Substance which has not so far been split up into a simpler form by ordinary chemical methods.

b) List, orderly arrangement, of facts, information, etc.

c) Branch of science that deals with how substances are made up, how they
(their elements) combine, how they act under different conditions.

6. Are the following statements true or false? Correct the false ones.

a) The Periodic Table consists of vertical periods and horizontal groups.

b) The properties of the elements are a periodic function of the nuclear charges of their atoms.

c) There were known 1044 elements at the time of publishing Mendeleev's Periodic Table.

d) The table contains 117 elements as of 27 January 2008 (elements 1—116 and element 118).

e) Mendeleyev's periodic system continues to form the basis for the most com­plex research.

7. Work in pairs: ask and answer questions.

A. What| rnodern| cornerstones| chemistry?

B.

A. How many| were| in 1869| elements| known?
B.

A. What| predict| Mendeleyev?
B.

A. What| enable| Periodic Table| to predict| scientists?

B.

8. Fill in the blanks using the words under the line.

a)One of the... of modern chemistry is the Periodic Law.

b)Mendeleyev arranged the elements in order of increasing atomic....

c)There were several... positions in Mendeleyev's periodic table.

d)In this table all the data about chemical elements are arranged into... sys­tem.

e)His name will be... in the discovery of new artificial elements.

IV. Supplement

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