II.2. Прочтите следующие вопросы и пометьте те из них, на которые вы можете ответить. Назовите номера вопросов, на которые вы затрудняетесь ответить.

1. What does all matter basically consist of?

2. What is a chemical element?

3. Can you name the most abundant elements in nature?

4. What is the total number of elements known today?

5. What do the properties of the chemical elements depend on?

6. What does the atomic number of an element indicate?

7. How is the ability of an atom to combine with another atom called?

8. How are the atoms held together?

9. What kinds of bonding do you know?

10. What is the Periodic Table of elements?

II.3. Прочтите текст а и найдите в нем ответы на «трудные» вопросы. Назовите номера вопросов в предыдущем упражнении, на которые вы ответили неправильно. Text a Chemical elements

A chemical element is any substance that cannot be decomposed into simpler substances by ordinary chemical processes. Chemical elements constitute the fundamental materials of which all matter consists. Of all the known elements, 90 occur in nature either chemically free or in combination with other elements.

About one-third of the elements found in nature occur in a chemically free state on Earth. These elements, which obviously are not very active chemically, include nitrogen, gold, platinum, copper, and the noble gases. The five most abundant elements in the Earth’s crust are oxygen (466,000 parts per 1,000,000, or 46.6 percent), silicon (27.7 percent), aluminum (8.1 percent), iron (5 percent), and calcium (3.6 percent). Hydrogen is by far the most abundant element in the universe, accounting for more than 90 percent of the total number of atoms and for about three-fourths of the mass. Helium is next in abundance, constituting about 7 percent of the number of atoms and nearly one-fourth of the total mass.

The properties of the elements are to a large degree attributable to the electronic structure and size of their atoms. Accordingly, they are extremely diverse. Helium, for example, has the lowest-known melting point (-271.4 ⁰C at 29.6 atmospheric pressure) and boiling point (-268.98 ⁰C) of any of the elements, while tungsten has the highest-known melting point (3,370 ⁰C) and boiling point (5,900 ⁰C).

The atomic number of an element indicates the number of protons (positively charged particles) in the nucleus of a given atom. It is also the number of electrons (negatively charged particles) in the atom that determines the chemical properties of the element. Each electron moves in an atomic orbit (equivalent to a particular energy level) around the nucleus.

The ability of an atom to combine chemically with another atom is called its valence. The valence of an element is the number of electrons it needs to gain or lose in order to make it stable. Atoms require a total of eight electrons in the outermost energy level to be stable in the case of the lightest atoms (hydrogen and helium) the number is two.

The way in which atoms are held together is known as bonding. The covalent bond is a type of chemical bond in which atoms are held together by shared pairs of electrons which move around both atoms. The electrovalent (or ionic) bond is another kind of chemical bond between atoms. Here, electrons are transferred from one atom to another forming ions. This produces electrostatic attraction; in other words, the attraction between opposite charges holds the ions together.

As the list of different elements grew in the 19^th century–by 1860 over 80 were known – chemists attempted to group them together and to classify them according to their behavior. In 1869 the Russian chemist Dmitri Ivanovich Mendeleyev made a complete table by arranging the elements in order of their atomic weights in rows so that elements with similar properties appeared in columns.

The Periodic Table produced by Mendeleyev was refined by further research into the structure of atoms. At present there are 110 known chemical elements. (The discovery of element 110, reported in 1987 by Soviet scientists, remains unconfirmed, however, and is still considered extremely tentative).

II.4. Прочтите и переведите текст А. Переведите абзацы 5 и 6 письменно.

II.5. Найдите в тексте английские эквиваленты названий следующих химических элементов: золото, кремний, медь, азот, алюминий, железо, кальций, водород, платина, гелий, кислород, благородные газы, вольфрам.

II.6. Дайте русские эквиваленты следующих слов и словосочетаний:

to occur in a chemically free state, chemically active, the most abundant element, the total mass, extremely diverse, a chemical bond, to be held together by shared pairs of electrons, the list of different elements, to arrange the elements in order of their atomic weights, elements with similar properties, to remain unconfirmed.

II.7. Найдите в тексте английские эквиваленты следующих слов и словосочетаний:

распадаться на более простые вещества; встречаться в природе; включать; самый распространенный элемент; составлять около ¾ от массы; составлять около 7%; атомное число; отрицательно заряженные частицы (электроотрицательные частицы); электроположительные частицы; способность соединяться; валентность элемента.

II.8. Дайте дефиниции следующих понятий:

atomic number

valence

bonding

a covalent bond

an ionic bond

the Periodic Table

II.9. Прочтите следующий текст о способности химического элемента к образованию органических химических соединений. Назовите элемент, название которого опущено в тексте.

The _____ atom is unique among elements in its tendency to form extensive networks of covalent bonds not only with other elements but also with itself. Because of its position midway in the second horizontal row of the periodic table, _____ is neither an electropositive nor an electronegative element; it therefore is more likely to share electrons than to gain or lose them. Moreover, of all the elements in the second row, _____ has the maximum number of outer shell electrons (four) capable of forming covalent bonds. (Other elements, such as phosphorus [P] and cobalt [Co], are able to form five and six covalent bonds, respectively, with other elements, but they lack _____ ability to bond indefinitely with itself.) When fully bonded to other atoms, the four bonds of the _____ atom are directed to the corners of a tetrahedron and make angles of about 109.5º with each other. The result is that _____ atoms not only can combine with one another indefinitely to give compounds of extremely high molecular weight, but the molecules formed can exist in an infinite variety of three-dimensional structures. The possibilities for diversity are increased by the presence of atoms other than _____ in organic compounds, especially hydrogen (H), oxygen (O), nitrogen (N), halogens (fluorine [F], chlorine [Cl], bromine [Br], and iodine [I]), and sulfur (S). It is the enormous potential for variation in chemical properties that has made organic compounds essential to life on Earth.