Материал: Аврамова NUCLEAR ENGLISH 2013

1. The idea of an atom came from ancient Greek science/philosophy.

The English word “atom” comes from the Greek word “atomos” meaning the smallest unit of matter. The idea of an atom was first proposed in 530 B.C. by Democritus, who thought that atoms were invisible and indivisible. We know it is not so, but we continue to use the word to designate the smallest particle which takes part in chemical interactions.

2.Every atom is electrically neutral and consists at least in part of equal amounts of positive and negative charge. The negative charge carriers in an atom are called electrons. The mass of an electron is very small compared to the mass of even the smallest atom (hydrogen). So, the question arises as to how the rest of the mass of the atom is distributed. If it is distributed uniform-

ly throughout the atom, then it should occupy а spherical volume whose radius is about 10-10 meters, which is the radius of any atom. But it is also possible that it is concentrated into a smaller volume inside the atom in a compact arrangement of mass and charge called a nucleus.

3.The notion that the positive charge in an atom is spread out uniformly in a sphere with a radius of 10-10 meters was advanced by the British physicist J. J. Thomson around 1900. In 1897, he was studying the relationship between electricity and matter. He carried out experiments with cathode rays. From his experiments Thomson concluded that cathode rays were made of tiny, negatively charged particles, which he called electrons. He believed that they came from inside the atoms. He also thought that because the electron was negatively charged and the atom was electrically neutral, there must be a positive charge somewhere in the atom.

4.From these results, Thomson proposed a model of the atom. In this model the positive charge carriers are uniformly distributed throughout the atom as a whole, and all the space in the atom is occupied by electrons and positive charge carriers. The Thomson model is often called the plum pudding model of the atom because the electrons which neu-

tralize the positive charge are supposed to be sсаtterеd around in the positive charge mass like plums in a plum pudding.

Exercise 1. Match the following Russian and English equivalents.

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Exercise 2. Complete the sentences with the words from Reading 1-A.

1.The atom is the smallest ______ which takes part in chemical

______.

2.The idea of an atom was first proposed by ______ in ______.

3.He thought that atoms were ______ and _______.

4.One of the early models of an atom was advanced by _______

at the end of the 19th century.

5.According to this model, the positive charge carriers are uniformly _________ throughout the atom.

6._______ are like plums in a plum pudding.

7.That is why the model is called the ____ ____ model.

Exercise 3. Give the derivatives of the words below.

1.To divide –деление, неделимый.

2.To act – взаимодействовать, взаимодействие.

3.To compare – сравнительный, по сравнению.

4.To arrange – расположение.

5.To relate to – отношение, относительный, относительность.

6.To conclude – вывод/заключение

7.To scatter– рассеяние.

8.To charge – заряженный, разрядить.

9.Sign – сигнал, конструировать, обозначать.

10.Chemistry – химический, химик.

11.Neutron – нейтральный, нейтрализовать.

12.Science – ученый, научный.

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Exercise 4. Read the text again and answer the questions below.

1.Where does the word "atom" come from? What does it mean?

2.Who proposed the idea of an atom?

3.What is the modern meaning of the word “atom”?

4.What is the charge of the atom? What is its size?

5.How does the mass of the electron compare with that of the atom?

6.What two hypotheses were put forward to explain the distribution of positive and negative charge in an atom?

7.What is the structure of the atom according to J.J. Thomson?

Time for Fun

Enjoy the joke:

Two atoms bump into each other. One says 'I think I lost an electron!' The other asks, 'Are you sure?' to which the first replies, 'I'm positive.'

Reading 1-B

The Rutherford Atom

"Your theory is crazy...but it's not crazy enough to be true."

(Niels Bohr)

The counter hypothesis that the positive charge carriers in an atom are not uniformly distributed throughout the atom but are concentrated in а small region at its centre is called the nuclear atom theory. The nuclear atom is often referred to аs the Rutherford atom after Ernest Rutherford who headed the team which carried out the first аlpha-particle

scattering experiments.

The Rutherford atom соnsists of а highly concentrated mass with а positive charge callеd the nucleus surrounded by negative charge carriers called electrons. Almost all the mass of the atom resides in the nucleus, which is composed of two different types of stable particles of almost equal mass, the proton which is posi-

tively charged and the neutron which is electrically neutral. The mass of the electron is 1/1836-th that of the proton, and although its charge is opposite in sign, it is numerically equal to that оf the proton. The number of planetary electrons in the electrically neutral atom is therefore

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equal to the number of protons in the nucleus. The chemical behavior of an atom is determined by its number of planetary electrons. Chemical combinations between atoms take place when combining atoms transfer or share outer electrons.

The Rutherford atom has аlsо been called the solar-system atom, since the concentration of mass in a nucleus surrounded by electrons reminds us of the sun-planet system in which we live. Actually, the differences between the solar system and the nuclear atom are much more scientifically significant than their similarities are. For example, the force which holds the planets in their orbits is gravitational, while the force which holds electrons in their orbits is elесtriсаl.

Exercise 1. Match the two parts of the sentences below. Look at

Reading 1-B to help you.

1.The nuclear-atom model was advanced by...

2.According to this model, the positive charge carriers...

3.Electrons are like...

4.Hence, another name of this model is ...

5.Actually, there is a great difference between...

6.The force that holds the planets together is gravitational,

while…

A. ....are concentrated in the nucleus and the electrons are revolving around the nucleus.

B. .... planets in the solar system.

C. ....the force that holds the atom together is electrical. D. ....Ernest Rutherford at the beginning of the 20th century. E. ....the solar-system model of the atom.

F. ….the nuclear atom and the solar system.

Exercise 2. Find the following international words in Reading 1-A and Reading 1-B. Copy them out.

Радиус, ядро, гипотеза, теория, модель, электрон, масса, орбита, положительный, нейтральный, электрический, стабильный, планетарный, солнечный, химический, гравитационный, концентрироваться, нейтрализовать.

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Exercise 3. Use Reading 1-B to find the English equivalents for the following Russian phrases.

Противоположная гипотеза, модель ядерного атома, солнечная система, проводить эксперименты, эксперименты по рассеянию альфа-частиц, состоять из, противоположный по знаку, численно равен, соединяться – химические связи, определять химическое поведение, передавать электроны, важное сходство.

Exercise 4. Match the two parts to make expressions from Reading 1-B. Read the text again if necessary.

Now complete these sentences using the expressions above.

1.The _____________ that the positive charge carriers in an atom are not _______________ throughout the atom but are concentrated in а small region at its centre is called the nuclear atom theory.

2.The nuclear atom is often referred to аs the Rutherford atom after Ernest Rutherford who headed the team which carried out the first

_____________.

3.Although the charge of the electron is ________, it is

_________ to that оf the proton.

4.The _________ of an atom is determined by its number of planetary electrons.

5.Chemical combinations between atoms take place when combining atoms ______ or share outer electrons.

Exercise 5. Read the text again and answer the questions below.

1.Who was the nuclear atom model proposed by?

2.Where are the positive charge carriers concentrated according to Ernest Rutherford?

3.What is the nucleus surrounded by?

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