Complete the sentences using the appropriate derivatives of the words in capitals.
1. Chemists accepted the periodic law immediately after its … /PROPOSE/.
2. Mendeleev made a very striking … of the periodic law /APPLY/.
3. The periodic law clearly indicated the … of neon, krypton, xenon and radon /EXIST/.
4. This … of the order in the periodic system caused much concern before the discovery of the atomic numbers of the elements /INVERSE/.
5. They discovered radon during the … of the properties of radium and other radioactive substances /INVESTIGATE/.
7. Translate the following sentences paying attention to the different meanings of the words "that" and "those".
1. Put your bag on that table. 2. Mendeleev found that the atomic weights were correlated with the properties of corresponding elements. 3. The atomic weight of potassium is 39.098 and that of argon is 39.948. 4. The inversion of the order in the periodic system from that of atomic weight caused much concern. 5. The properties of the elements and those of their compounds are close to those predicted by Mendeleev. 6. That difficulty exists no more. 7. The properties of those compounds are different. 8. Elements from Group I differ from those of Group II.
Put questions of different types to the following sentences.
1. Mendeleev proposed a periodic table containing seventeen columns. 2. Chemists added the "zero" group to the periodic table after the discovery of helium, neon, argon, krypton and xenon by Lord Rayleigh and Sir William Ramsay. 3. Most of the elements occur in the periodic table in the order of increasing atomic weights. 4. Mendeleev made a very striking application of the periodic law. 5. He predicted the existence of six elements which scientists discovered later.
Translate the sentences into English. Mind Past Tenses .
1. Когда Менделеев разрабатывал периодическую систему, учёные еще не открыли многих элементов. 2. Учёные основали Русское химическое общество в 1868 году. 3. Химики добавили нулевую группу к периодической таблице после того, как открыли инертные газы. 4. Последующие открытия новых элементов подтвердили предсказания Менделеева. 5. Учёные открыли гелий, неон, аргон, криптон и ксенон в 1894 году и в последующие годы. 6. Всю свою жизнь Менделеев посвятил развитию науки. 7. Химические свойства указывали на нарушение порядка в нескольких местах в таблице. 8. Менделеев предсказал существование шести элементов, которые учёные открыли гораздо позже.
|
|
|
Answer the following questions.
1. When did Mendeleev present his periodic table?
2. How many columns did it contain?
3. Why did Mendeleev revise his periodic table?
4. What elements are there in "zero" group?
5. How did Mendeleev arrange elements in the system?
6. What elements are there in the inverted order of atomic weight?
7. What discoveries verified Mendeleev's predictions?
Section II
TEXT B
Notes on the text:
array – массив, множество, таблица; coincide – совпадать; signify – означать; level – уровень; traverse – перемещаться; infer – делать вывод, заключать; behave in a similar fashion – вести себя подобным образом; familiar with – знакомый с; determine a significant amount – определить значительное количество
1. Skim the text and entitle its paragraphs.
THE PERIODIC TABLE OF THE ELEMENTS
The periodic table is the most important chemistry reference. It arranges all the known elements in an informative array. Chemists arranged elements left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass.
The different rows of elements are called periods. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state). The number of electrons in a period increases as one traverses down the periodic table; therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.
|
|
|
Using the data in the table scientists, students, and others that are familiar with the periodic table can extract information concerning individual elements. For instance, a scientist can use carbon's atomic mass to determine how many carbon atoms there are in a 1 kilogram block of carbon.
People also gain information from the periodic table by looking at how it is put together.By examining an element's position on the periodic table, one can infer the electron configuration. Elements that lie in the same column on the periodic table (called a "group") have identical valence electron configurations and consequently behave in a similar fashion chemically. For instance, all the group 18 elements are inert gases. The periodic table contains an enormous amount of important information. People familiar with how the table is put together can quickly determine a significant amount of information about an element.
Дата добавления: 2019-01-14; просмотров: 239; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!