The Atomic Model

The electron, the proton, and the neutron gather together into what can be called the atom.

Our concept of the atom derives from a series of observations. As a result of these observations, we now believe that an atom is composed of a cloud of electrons that revolve about a central core of protons or of protons plus neutrons. Repeated experiments, which were referred to above, show that every atom has the same number of electrons as well as protons. The positively charged protons form the nucleus of the atom, and balance the positive charges of the protons in the core of the atom. The neutrons are also found in the nucleus of the atom^: 'An atom has already been spoken of as the smallest unit of an element.

It is known that ninety-two elements occur in nature, and a number of others have been made by man in the laboratory. Every element is a special combination of protons, neutrons, and electrons. Each element is identified by the number of protons in its nucleus and is designated by a name and a symbol.

Element Number I is a combination of one proton and one electron. Long before its atomic structure was known, this element was referred to as hydrogen, or "water-former", because water forms when hydrogen burns in air. Its symbol is H. Hydrogen has first place in the list of elements because it has one proton in its nucleus. Element 1 is followed by Element Number 2. It consists of two protons and two electrons. It was named helium, with the symbol He

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Ex. 5 Дайте відповіді на питання

1. What is an atom? 2. What does it mean if atoms cannot be seen? 3. What methods are used to determine the sizes of atoms? 4. What is the radius of an atom? 5. To what con­clusion did the chemists come? 6. What structural units do the atoms contain? 7. What space do the electrons fill? 8, How can the numbers of electrons, protons, and neutrons in an atom be calculated? 9, How many elements occur in nature? 10. Why is Element Number 1 referred to as "water-former"?

Ex. 6 Перекажіть текст використовуючи наступний план.

1. The definition of an atom.

2, The methods by means of which it is possible to determine the size of an atom.

3. The size of an atom.

4, Three simple types of units

5. The diagram showing the constituents of an atom.

6. The position and numbers of the structural units in an atom.

7. The numbers of electrons.

8. The number of elements occurring in nature

Ex. 7. Перекладіть речення.,

1. According to the atomic theory this means that the number of atoms of carbon in combination with the same num­ber of atoms of oxygen is two times as great in carbon monoxide as in carbon dioxide. 2. The velocity of a reaction means the amount of the material which undergoes change in unit time. 3.The heterogeneity of a substance may be shown by differ­ent means. 4. Fractional distillation is used extensively in chemical industry as a means of separating and purifying many products. 5. The average distance through which a molecule moves between collisions is called the mean free path. 6. The kinetic theory makes it possible to calculate the mean ve­locity of molecules.

Ex. 8. Відкрийте дужки. Перекладіть речення.

1. Atoms are not (smaller, the smallest) particles, but they are very small. 2. This discovery is (more important, the most important) than the previous one. 3. It is much (easier, the easiest) to make parts of plastics than of metal or wood. 4. This is (better, the best) laboratory in our Institute. 5. Aluminium is (lighter, the lightest) known metal. 6. Hydrogen is (lighter, the lightest) of the elements. 7. Beryllium is (less, the least) active member of the group, and there is a regular increase in activity from metal to metal in the order of increased atomic numbers. 8 (More, the most) characteristic chemical property of hydrogen peroxide is its great oxidizing power.

Ex. 9Перекладіть речення.

1. Electrons have been spoken of as moving in orbits about the atomic nucleus. 2. This law is generally spoken of as the Second Law of Thermodynamics. 3. It had already been mentioned that many of the elementary gases couid exist in diatomic molecules. 4. In general the oxidation number may be thought of as an electrical charge of the atom. 5. The results of our work will be discussed at the conference. 6. A base is referred to as a substance that accepts protons from another substance. 7. It has been noted that chlorine dioxide reacts with water. 8. The sodium salt is being manufactured in industrial quantities. 9. This method is being used in our laboratory. 10.' The Institute was being built when we came to this town

Ex. 10Перекладіть речення.

An atom is the smallest possible particle of any substance. Before, atoms were looked at as the smallest particles that can exist. But now it has been proved that atoms have a complicat­ed internal structure which is composed of particles which are much smaller still. When we say that an atom is the smallest particle of any substance, we mean that atom is the basic unit of a substance.

Ex. 11 Перекладіть речення.

1. In the dye solution most dyes go into colloidal suspen­sion. 2. In most carbon compounds only one valence bond is held between adjacent carbon atoms. 3. The discovery of steel was one of the most important inventions of man, for it gave him one of the hardest materials. 4. In the atmosphere oxygen is for the most part uncombined. 5. Most of the interior of an atom can be considered as an empty space, similar to that between the planets. 6. Many ions, probably most of them, are hydrated in aqueous solution. 7. The most convenient method was that used by our scientists. 8. The most extensive use of ammonium sulphate is in plant fertilizers. 9. Most of our students take an active part in the preparation for this conference. 10. Unlike most salts the solubility of anhydrous salt decreases with the rise in temperature.

Ex. 12 Прочитайте текст передайте його основний зміст