Answer the following question.

Lead-in

· What is the periodic table of elements?

· What do you know about the scientists who elaborated the periodic table?

· Why is the periodic table of elements so important for chemists?

Pronunciation tips

1.	actinide	['æktɪnaid]	8.	nucleus	['njuːklɪəs]
2.	actinium	[æk'tɪnɪəm]	9.	scandium	['skændɪəm]
3.	atomic	[ə'tɔmɪk]	10.	to spur	[spɜː]
4.	gallium	['gælɪəm]	11.	sulphur BrE. (sulfur AmE.)	['sʌlfə]
5.	germanium	[ʤɜː'meɪnɪəm]	12.	to synthesize	['sɪnθəsaɪz]
6.	lanthanide	['lænθənaid]	13.	weapon	['wepən]
7.	lanthanum	['lænθənəm]	14.	ununnilium	[ˌuːnəˈnɪliəm] or [ˌʌnəˈnɪliəm]

THE PERIODIC TABLE


Dmitri Mendeleev	Henry Moseley
(8 February 1834 – 2 February 1907)	(23 November 1887 – 10 August 1915)

Early civilizations were familiar with a few of the substances now called elements. They made coins and jewellery from gold and silver. They also made tools and weapons from copper, tin, and iron. In the nineteenth century, chemists began to search for new elements. By 1830, they had isolated and named 55 different elements. The list continues to grow today.

A Russian chemist, Dmitri Mendeleev, published the first version of his periodic table in the Journal of the Russian Chemical Society in 1869. Mendeleev arranged the elements in order of increasing atomic mass. Elements with similar properties fell into groups on the table. At that time not all the elements were known. To make his table work, Mendeleev had to leave three gaps for missing elements. Based on the groupings in his table, he predicted the properties of the missing elements. Mendeleev’s predictions spurred other chemists to look for the missing elements. Within 15 years, these elements (gallium, scandium, and germanium) were discovered.

Although Mendeleev’s table correctly organized most of the elements, a few elements seemed out of place. In the early twentieth century, the English physicist Henry Moseley realized that Mendeleev’s table could be improved by arranging the elements according to atomic number rather than atomic mass. Moseley revised the periodic table by arranging the elements in order of increasing number of protons in the nucleus. With Moseley’s table, it was clear how many elements were still undiscovered.

In the modern periodic table the elements still are organized by increasing atomic number. A period is a row of elements in the periodic table which properties change gradually and predictably. The periodic table has 18 columns of elements. Each column contains a group of elements. A group contains elements that have similar physical or chemical properties. Zones on the Periodic Table The periodic table can be divided into sections. One section consists of the first two groups, groups 1 and 2, and the elements in groups 13-18. These eight groups are the representative elements. They include metals, metalloids, and non-metals. The elements in groups 3-12 are transition elements. They are all metals. Some transition elements, called the inner transition elements, are placed below the main table. These elements are called the lanthanide and actinide series because one series follows the element lanthanum, and the other series follows actinium.

The symbols for the elements are either one- or two-letter abbreviations, often based on the element name (e.g. S for sulphur, Sc for scandium). Sometimes the symbols don’t match the names (e.g. Ag for silver). Newly synthesized elements are given a temporary name and 3-letter symbol that is related to the element’s atomic number (e.g. Uun for ununnilium). The International Union of Pure and Applied Chemistry (IUPAC) adopted this system in 1978. Once the discovery of the element is verified, the discoverers can choose a permanent name.

Answer the following question.

1. What elements have been known since the ancient times?

2. Why did D. Mendeleev leave empty spaces in his periodic table?

3. How did H. Mosley suggest rearranging the original version of the periodic table?

4. What is the structure of the modern periodic table?

5. Why were some elements given the temporary names?

Match the key concepts of the periodic table with the corresponding definitions.

1.	alkali metals	a)	element in the d-block of the periodic table, which includes groups 3 to 12.
2.	alkaline-earth metals	b)	under standard conditions, they are all odourless, colourless, monatomic gases with very low chemical reactivity.
3.	transition elements	c)	somewhat reactive metals at standard temperature and pressure and readily lose their two outermost electrons to form cations with charge ⁺2.
4.	inner transition elements	d)	chemical elements with properties that are in-between or a mixture of those of metals and non-metals.
5.	noble gases	e)	shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge ⁺1.
6.	halogens	f)	the f-block of the periodic table, are also called the lanthanide and actinide series because one series follows the element lanthanum, and the other series follows actinium.
7.	metalloids	g)	a group in the periodic table consisting of five highly reactive elements; in the modern IUPAC nomenclature, this group is known as group 17.

Define the location of alkali metals, alkaline-earth metals, transition elements, inner transition elements, noble gases, metalloids and halogens on the periodic table.

Word search

Find synonyms to the following words and word groups in the text

1. an instrument, a piece of equipment (para 1)

2. to look for, to seek (para 1)

3. to put in order, to classify, to organize (para 2)

4. breach, space (para 2)

5. to encourage, to inspire (para 2)

6. a characteristic feature, a peculiarity (para 2)

7. to enhance, to upgrade (para 3)

8. to rise, to extend (para 3)

9. to confirm, to validate (para 5)

10. to correspond, to conform (para 5)

Find words corresponding to the definitions below.

1. to issue printed textual material for sale or distribution to the public (para 2)

2. to foretell the future (para 2)

3. to be the first to find or find out about something (para 2)

4. to grasp or understand clearly (para 3)

5. an element that has both metallic and non-metallic properties (para 4)

6. existing for an indefinite period of time (para 5)

7. a shortened form of a word or phrase (para 5)

8. lasting for a short period of time (para 5)

Date: 2015-12-24; view: 1125

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