ВУЗ:
Составители:
Рубрика:
13
II. Answer these questions.
1. How many elements did Mendeleyev describe?
2. When did Mendeleyev publish his Periodic Table?
3. When did Mendeleyev finish school?
4. Where was World Chemical Congress in 1860?
5. When did Mendeleyev receive Master degree?
III. Retell the text.
14
TOPIC 3
I. Read and translate the text.
THE PERIODIC TABLE
The periodic recurrence of properties of the elements with increas-
ing atomic number may be effectively emphasized by arranging them in
a table called the periodic table or periodic system of the elements. Sev-
eral alternative forms of the periodic table have been proposed and used.
I would like to tell about the development of the periodic table. A
long time was required for the recognition of the fact that all the elements
can be classified in the way now described by the periodic law. The most
important step in the development of the periodic table was taken in
1869, when the first Russian chemist Dmitri Mendeleyev made a thor-
ough study of relation between the atomic weights of the elements and
their physical and chemical properties. He proposed a periodic table con-
taining seventeen columns, with end columns (labeled 0) missing (these
elements had not yet been discovered at that time). In 1871 Mendeleyev
and the German chemist Meyer, who was working independently, pro-
posed another table, with eight columns, obtained by splitting each of the
long periods into a period of seven elements. The periods were later dis-
tinguished by use of letters “a” and “b” attached to the group symbols,
which were the Roman numerals.
The periodic table in the second form, proposed by Mendeleyev
(the “short-periodic” form), remained popular for many years, but has
now been largely replaced by the “long-periodic” form, which is in better
agreement with the new knowledge about the electronic structure of at-
oms.
In 1871 Mendeleyev found that by changing seventeen elements
from the position indicated by the atomic weights that had then been as-
signed to them into new positions, their properties, could be better corre-
lated with the properties of the other elements. Further experimental
work verified Mendeleyev’s revisions.
He was able to predict the existence of six elements that had not
yet been discovered, corresponding to vacant places in his table. He
named these elements eka-boron, eka-aluminum, eka-silicon, eka-
manganese, dvi-manganese, and-tantalum.
II. Answer these questions. TOPIC 3
1. How many elements did Mendeleyev describe?
I. Read and translate the text.
2. When did Mendeleyev publish his Periodic Table?
3. When did Mendeleyev finish school?
THE PERIODIC TABLE
4. Where was World Chemical Congress in 1860?
5. When did Mendeleyev receive Master degree? The periodic recurrence of properties of the elements with increas-
ing atomic number may be effectively emphasized by arranging them in
III. Retell the text. a table called the periodic table or periodic system of the elements. Sev-
eral alternative forms of the periodic table have been proposed and used.
I would like to tell about the development of the periodic table. A
long time was required for the recognition of the fact that all the elements
can be classified in the way now described by the periodic law. The most
important step in the development of the periodic table was taken in
1869, when the first Russian chemist Dmitri Mendeleyev made a thor-
ough study of relation between the atomic weights of the elements and
their physical and chemical properties. He proposed a periodic table con-
taining seventeen columns, with end columns (labeled 0) missing (these
elements had not yet been discovered at that time). In 1871 Mendeleyev
and the German chemist Meyer, who was working independently, pro-
posed another table, with eight columns, obtained by splitting each of the
long periods into a period of seven elements. The periods were later dis-
tinguished by use of letters “a” and “b” attached to the group symbols,
which were the Roman numerals.
The periodic table in the second form, proposed by Mendeleyev
(the “short-periodic” form), remained popular for many years, but has
now been largely replaced by the “long-periodic” form, which is in better
agreement with the new knowledge about the electronic structure of at-
oms.
In 1871 Mendeleyev found that by changing seventeen elements
from the position indicated by the atomic weights that had then been as-
signed to them into new positions, their properties, could be better corre-
lated with the properties of the other elements. Further experimental
work verified Mendeleyev’s revisions.
He was able to predict the existence of six elements that had not
yet been discovered, corresponding to vacant places in his table. He
named these elements eka-boron, eka-aluminum, eka-silicon, eka-
manganese, dvi-manganese, and-tantalum.
13 14
Страницы
- « первая
- ‹ предыдущая
- …
- 5
- 6
- 7
- 8
- 9
- …
- следующая ›
- последняя »
