Introduction into chemistry.

Part Two

A chemical element is a substance that cannot be divided into smaller chemical parts. The smallest particle of such an element is an atom. Atoms are made up of protons, neutrons, and electrons. A pure element contains only one kind of atom. The number of protons in the atoms of an element is known as that element's atomic number. For example, all atoms with 6 protons in their nuclei are of the chemical element carbon, and all atoms with 92 protons in their nuclei are of the element uranium.117 different chemical elements are known to modern chemistry. 90 of these elements can be found in nature, and the others can only be made in laboratories. The first man-made element was Technetium in 1937. All man-made elements are radioactive and unstable.Chemical elements are commonly arranged in the periodic table. Atoms of the same element, whose nuclei contain a different number of neutrons, are said to be different isotopes of the element. Chemical elements are also given a unique chemical symbol. Chemical symbols of elements come from their English or Latin names (For example, carbon has the chemical symbol 'C', and sodium has chemical symbol 'Na', after the Latin natrium). Elements can combine (react) to form pure compounds (such as water, salts, oxides, and organic compounds). In many cases, these compounds have a fixed composition and their own structure and properties. Some elements, particularly metal elements mix together in any proportion to form new structures. Such new structures are not compounds. They are called mixtures.

Classification. Elements can be classified based on physical states. At room temperature and pressure, most elements are solids, only 11 are gases and 2 are liquids. Elements can also be classified into metals and non-metals. There are many more metals than non-metals. However, a few elements have properties in between those of metals and non-metals (semi-metals). A chemical compound is a chemical made by joining together atoms of different chemical elements. The different atoms stick together so strongly that the compound behaves like one kind of substance. What it is made of depends on how the atoms are joined together. Chemical compounds can be liquids, like water which is made from atoms of hydrogen and oxygen joining together. They can also be solids, like salt. Some chemical compounds are natural, which means that they are not made by people. Some chemical compounds, often called just chemicals, are synthetic, which means they made by people using machines. Sometimes when a person mixes together two different liquids, they can turn into a different liquid that is not anything like the ones he or she started with. A person can also sometimes mix powder into a liquid to make a new liquid. This is called 'chemistry'.

Exercise 1. Translate from English into Russian.

1. We know three physical states of the elements: solids, liquids and gases.

2. Only 90 elements of the periodic table are really met in nature, others are made artificially by humans.

3. An isotope - is the atom of an element with nuclei containing a different number of neutrons.

4. Each chemical element has its English or Latin name according to which a chemical element is given its chemical symbol.

5. Water is a liquid chemical compound made from atoms of hydrogen and oxygen.

Exercise 2. Translate into English

химический элемент, вещество, атом, ядро, современная химия, лаборатория, радиоактивный, изотоп, оксид, свойства, давление, твердые вещества, жидкие вещества.

1. В природе найдены 90 химических элементов из периодической таблицы.

2. Атом - мельчайшая частица химического элемента, состоящая из протонов, нейтронов и электронов.

3. Каждый химический элемент имеет свой символ.

4. Химические элементы образуют соединения, имеющие собственную структуру и свойства.

5. Химические элементы классифицируются согласно их физическому состоянию; также их можно разделить на металлы и неметаллы.

Exercise 3. a) Give one word for each of the following

- a substance indivisible into smaller chemical parts

- the smallest particle of an element

- the number of protons in the atom of an element

- a unique sign given to each chemical element

- new structures in which some elements are mixed together in any proportion

- a chemical made by joining together atoms of different chemical elements

b) Explain in your own words: The periodic table, man-made elements, natural elements, physical state, chemical

Exercise 4. Answer the questions.

1. What is an atom? What does it consists of?

2. What is the difference between natural and man-made elements?

3. Give the definition of an isotope.

4. What is a chemical symbol? How do elements get their symbols?

5. Give examples of pure compounds.

6. How can elements be classified?

7. What have you learnt about chemical compounds?

Exercise 3. Divide the text into several passages. Give a key-sentence to each passage. Give the main idea of each passage in short.

Exercise 4. Make the summary of the text.

Branches of chemistry

Read the text about branches of chemistry. Find the passage which contains the information about organic and inorganic chemistry. Read and translate the passage.

Chemists have divided chemistry into a number of different branches. These branches often overlap with each other or with other sciences, such as physics, geology, or biology. Inorganic chemistry is the study of the chemical nature of the elements and their compounds. Organic chemistry is the study of compounds consisting largely of hydrocarbons, which provide the parent material of all other organic compounds. Since carbon atoms can form rings and long branched chains, hundreds of thousands of carbon-based molecules exist. Organic chemists have learned how to convert raw materials from coal, petroleum, and grain into synthetic textiles, pesticides, dyes, drugs, plastics, and many other products.

Radiochemistry is the study of the chemical effects of high-energy radiation and the behavior of radioactive isotopes, atoms of the same element that vary in the number of neutrons they contain.

Physical chemistry is fundamental to all chemistry and deals with the application of physical laws to chemical systems and chemical change. Much of physical chemistry is concerned with the role of energy in chemical reactions; this branch of physical chemistry is known as thermodynamics. Other major areas of study in physical chemistry are the rates and mechanisms of reactions, called chemical kinetics. A third area of physical chemistry studies molecular structure. Physical chemists study molecular structure by examining the spectrum of electromagnetic energy emitted by molecules and explain structure using principles of quantum mechanics.

Analytical chemistry is the science of separating complex materials into simpler ones and detecting and measuring the constituents. It is the oldest branch of chemistry. A major feature of chemical analysis today is the wide use of physical instruments and computer control to automate the analysis of complex materials.

Biochemistry is the chemistry of living organisms and life processes. Even the simplest living thing is a complex chemical factory. Biochemists must have a detailed knowledge of organic chemistry. Geochemistry is the application of chemistry (and, inevitably, physics) to processes taking place in the earth, such as mineral formation, the metamorphosis of rocks, and the formation and migration of petroleum. Fields such as biochemistry, geochemistry, and materials science reveal the unity of the sciences.

Vocabulary

Hydrocarbon, parent material, branched chain, to convert, to grain, dye, pesticide, quantum mechanics, to measure, petroleum, material science.

Task

I. Write down all the branches of chemistry met in the text. Think of the activities the scientists in each field may do.

II. Give the summary of the text.

 

Unit 2 Chemical Elements

 

The Periodic Table

The periodic table of the chemical elements is a list of known atoms (chemical elements). In the table the elements are placed in the order of their atomic numbers starting with the lowest number. The atomic number of an element is the same as the number of electrons or protons in the atom. In the periodic table the elements are arranged into periods and groups. A row of elements across the table is called a period. Each period has a number: from 1 to 7. Period 1 has only 2 elements in it: hydrogen and helium. Period 2 and Period 3 both have 8 elements. Other periods are longer. A row of elements down the table is called a group. There are 18 groups in the standard periodic table. Each group has a number: from 1 to 18. Elements in a group have electrons arranged in similar ways, which gives them similar chemical properties (they behave in similar ways). For example, group 18 is known as the noble gases because they are all gases and they do not combine with other atoms. The periodic table can be used by chemists to observe patterns, and relationships between the elements. For example, elements to the top and far left of the table are the most metallic, and elements on the bottom right are the least metallic. (e.g lithium is much more metallic than xenon).

 The Periodic Table was invented and arranged by the Russian chemist Dmitri Mendeleev (1834-1907). He was the first to think of the table. Lots of atoms that have higher numbers are radioactive, like radium and uranium, and should never be handled without a lot of care and protection because they give off so much radiation.The simplest atom is the hydrogen atom, which has atomic number 1. The most common type of hydrogen atom has 1 proton and 1 electron (with no neutron). The hydrogen isotope containing 1 additional neutron is called deuterium; the hydrogen isotope with 2 additional neutrons is called tritium. The periodic table helps chemists to remember the similarities and gradation of properties within element groups. The discovery of the periodic law and publication of this table in 1869 was a major step in organizing information about the known elements and in predicting the properties of unknown ones.

Chemical Series of the Periodic Table

• Alkali metals
• Alkaline earths
• Lanthanides
• Actinides
• Transition metals
• Poor metals
• Metalloids
• Nonmetals
• Halogens
• Noble gases

Exercise 1. Read the words and learn their pronunciation

/eı/ table, atom, relation, radioactive, arrange, behave

/əu/ protons, unknown, noble

/e/ element, electron, invent, protection

/æ/ gas, metallic, patterns, halogen

/ə/ atomic, lithium, across, combine

/u:/ group, neutral

/aı/ type, hydrogen, organizing

/k/ chemical, chemist, predict

/ʃ/ radiation, relationships, protection, Russian, additional

Exercise 2. Learn the new words

Row, chemical properties, noble gases, radioactive, periodic law, alkali, alkaline, transition, halogen.

Exercise 3. Answer the questions.

2) Give the definition of the periodic table.

3) What does the atomic number show?

4) How are elements arranged in the periodic table?

5) What elements does Period 1 have?

6) How much groups are there in the standard periodic table?

7) What can you say about noble gases?

8) Who invented and arranged the periodic table?

9) What can you say about the elements with higher numbers?

10) What is the simplest element of the table? Tell about its isotopes.

11) What is the meaning of the periodic table?

Exercise 4. Divide the text into several passages. Give a key-sentence to each passage. Give each passage its title.

Exercise 5. Retell the text

Atom

Read the text about atoms and speak about

a) the structure of atoms

b) atoms’ possible characteristics

 

 

An atom is the most simple type of particle that makes up matter. Matter is anything that has mass and uses space. It is the smallest part of an element that still has the properties of that certain element. Atoms are made of 3 kinds of sub-atomic particles - protons, neutrons and electrons. A proton has a positive charge. A neutron has no charge. An electron has a negative charge. Electrons have much less weight than the protons and neutrons and move very fast around the nucleus. In a neutral atom, the number of protons is the same as the number of electrons. Charged atoms are called ions. Atoms with fewer electrons than protons have a positive charge and are called cations. Atoms with more electrons than protons have a negative charge and are called anions.

Structure. The nucleus is at the center of an atom. It contains protons and neutrons, which are tightly packed together. Because of this, the nucleus is positively charged. Protons and a neutrons have similar mass. The nucleus of an atom is very small. Most of an atom is empty space which is occupied by electrons spinning around.

Classification. Atoms are usually put into groups based on their atomic number. The atomic number of an atom is the number of protons in the atom. The atomic number decides what family or "element" the atom belongs to. All atoms with the same atomic number share many of physical properties and have the same chemical behavior. The different kinds of atoms are listed in the Periodic table. The mass number or "nucleon number" is the total of protons and neutrons. The number of neutrons does not change the element of the atom - within an element family are several members, each with the same atomic number but different mass numbers. These are called isotopes. To write the name of an isotope, we write the name of an element, then its mass number. Radioactive atoms and isotopes are dangerous to any living thing except in very small amounts. They should only be handled by experts because they can make people very sick if not handled correctly. Doctors sometimes use isotopes. For example, the isotopes of Barium and Iodine are used to help find illnesses. Only 94 different types of atoms are found in nature, A few more have been made in laboratories). All matter and all substances are made up of these kinds of atoms. Most things contain far fewer types of atoms. Water, for example, contains only atoms of hydrogen and oxygen. In water these atoms form combinations called molecules.

Molecules

Read the text about molecules and speak about

a) the way atoms are stuck together in a molecule

b) the break of the bonds

A molecule is the smallest amount of a chemical substance that can exist. If a molecule were split into smaller pieces, it would be a different substance. Molecules are made up of atoms that are stuck together in a particular shape or form. Not all combinations of atoms are usually possible; atoms like certain shapes, but not others. For example, oxygen atoms always have two bonds with other atoms, carbon atoms always have four bonds with other atoms, and nitrogen atoms always have three bonds with other atoms. In gases like air, the molecules are just flying around. In liquids like water, the molecules are stuck together but they can still move. In solids like sugar, the molecules can only vibrate. With a molecular formula, you can write down the numbers of all atoms in a molecule. For example, the molecular formula of sugar is C₆H₁₂O₆. That means that one molecule of sugar is made up of six carbon atoms, twelve hydrogen atoms and six oxygen atoms.

Bonding

For a molecule to exist, atoms have to stick together. This happens when two atoms share electrons. Instead of circling just one atom, the electron now circles around two. This is called bonding. The shared electrons are called 'bonds'. Sometimes, more than one electron is shared. The more electrons are shared, the stronger the bond gets and the stronger the atoms stick together. Bonds can also be broken apart. Since most bonds require energy to form, they also give off energy when they are broken. But before most bonds break, the molecule has to be heated. Then the atoms start to move, and when they move too much, the bond breaks. Molecules that require less energy to break than they give off when broken are called fuels. For example, a candle will just sit there and nothing happens. But when you use a match to light it, it will burn for a long time. The match brings the energy to break the first bonds, which release enough energy to break the bonds below them, until the candle has burned down.

 

 

Unit 3 Inorganic Chemistry

For correct naming the elements see the appendix for chemistry which includes the list of the names of chemical elements in English.

molecule - молекула

diatomic - двухатомный

single – единичный

subscript – подстрочный индекс

polyatomic - многоатомный

numerical – числовой

corresponding - соответствующий

sulphur – cepa

covalent - ковалентный

unlik е – различный

similar – подобный

hydrogen chloride - хлористый водопро-

вод

electropositive – электроположительный