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THE PERIODIC TABLE OF ELEMENTS (II)






 

When all of the metals are to be considered as a group, an advantage may be gained if their names are set down in tabular form. This table is a modification of an arrangement made by the Russian chemist Mendeleyev about 1870. This table shows the known elements in the order of the strength of the electrical charge on their nuclei, or inner portions. Elements in the same column are usually similar chemically. At least 88 of the first 92 elements are found in nature. Elements 93 and above were produced synthetically during and after the development of the atomic bomb.

In the table the elements are placed in the order of the strength of the positive electrical charge on the nuclei of their atoms. This strength is indicated by the number in the box above each element. Not only does this number, called the “atomic number”, indicate the charge on the nucleus but it specifies, also, the number of electrons surrounding the nucleus. The combined charge of the electron “cloud” – that is, the outer portion of the atom – must be equal in magnitude and opposite in sign to the charge on the nucleus. Otherwise, the atom would not be electrically neutral. The nature of the electron cloud is very important because it determines the chemical and physical properties of the element.

The table makes possible a quick determination of whether an element is a metal or a non-metal. Elements to the left of the heavy, stepped line near the right of the table are metals. Elements to the right of this line are not metals although those immediately to the right, boron, silicon, selenium, tellurium and polonium, are sufficiently metal-like to be called “metalloids”.

While the periodic table is being considered, two points of historical interest may be mentioned. The first refers to the names of metals. One notes that many of the names end in “-ium”. They are the more recently discovered metals, mainly those found in the nineteenth and twentieth centuries. The metals known to the ancient world and those discovered in later times into the eighteenth century were named before the -ium system was established. Examples of such metals are iron, lead, copper, and zinc.

The second point concerns “naturally occurring” and “artificial” elements. With the exception of numbers 43, 61, 85, and 87, all of the elements up to and including 92, uranium, have been found in nature, mainly in ores. Some doubt exists as to whether elements 43 and 61 occur naturally. If they do, the amounts are near the limit of detectability. The four elements mentioned and all of those with numbers higher than 92 have been produced artificially during research related to atomic weapons and nuclear reactors. Including those made artificially, 103 elements are known, of which approximately 75% are metals.



 

2. Find in the text English equivalents to the following words and word combinations:

отримувати перевагу, модифікація, електричний заряд, внутрішні частини, електрон, ядро, швидке визначення, “штучні” елементи, атомна зброя.

 

3. Make up word combinations from the following words and translate them into Ukrainian:

portions, artificial, cloud, atomic, electrical, number, charge, inner, electron, elements.

 

4. Find in the text antonyms to the following words:

disadvantage, different, negative, unequal, natural.

 

5. Combine the following simple sentences into a complex ones by using relative pronouns who, which, that:

 

who (used for people), which (used for things), that (used for people and things)

 

1. This table is a modification of an arrangement. It was made by the Russian chemist Mendeleyev.

2. The strength is indicated by the number in the box above each element. The number is called as “the atomic number”.

3. Mendeleyev was the greatest Russian chemist. He arranged the table of elements in the order of the strength of the electrical charge.

4. The strength is indicated by the number in the box. It can be seen above each element.

5. The table makes possible a quick determination of elements. Elements are indicated as metals and non-metals.

 

6. Complete the following sentences by adding a clause:

1. Mendeleyev declared that …

2. He said that elements ...

3. Scientists discovered that …

4. He declared that the table …

5. The reporter mentioned that …

6. One notes that …

 

7. Complete the following sentences by adding the clauses:

1. An advantage may be gained if ...

2. Two points of historical interest may be mentioned while …

3. The nature of the electron cloud is very important, because …

4. Elements to the right of this line are not metals although ...

 


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