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प्रश्न
Write a short note.
Position of isotopes in the Mendeleev’s and the modern periodic table.
उत्तर
Isotopes: Isotopes are the atoms having the same atomic number but different atomic masses.
Therefore, according to Mendeleev’s classification, these should be placed at different places depending upon their atomic masses.
For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties. So this was a drawback of Mendeleev's periodic table as he could not explain the position of isotopes.
The modern periodic table is based upon the arrangement of the elements on the basis of their atomic number. So, all the isotopes of hydrogen should be placed at the same place depending upon their atomic number.
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संबंधित प्रश्न
Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?
Consider the following elements:
Na, Ca, Al, K, Mg, Li
Which of these elements belong to the same group of the periodic table?
Which element has two shells, both of which are completely filled with electrons?
How does the chemical reactivity of the halogens vary on going in group 17 of the periodic table?
State how the valency of elements varies in a period of the periodic table?
On the basis of electronic configuration, how will you identify the first element of a period?
What is the number of elements is 1st period the modern periodic table?
Helium and neon are unreactive gases. What, if anything, do their atoms have in common?
The atomic numbers of the three elements X, Y and Z are 2, 6 and 10 respectively.
(i) Which two elements belong to the same group?
(ii) Which two elements belong to the same period?
Give reasons for your choice.
Correct the statement.
Transition elements are placed at extreme right of the periodic table.
What do you understand by typical elements?
Fill in the blank:
The horizontal rows in the periodic table are called _____________.
What is the number of elements in the 3rd period, of the modern periodic table?
An element A has 2 electrons in its fourth shell. State its electronic configuration.
Give the symbol and valency of the following element and radical.
Nitrate
Give the chemical formula of sodium hydroxide
Give the chemical formula of sodium nitrate
Give the chemical formula of calcium phosphate
Fill in the blank:
The element lithium in the Modern Periodic Table with valency 1+ belongs to the group ______.
State the number of elements in Period 1 of the Periodic Table.
State the number of elements in Period 3 of the Periodic Table.
How were elements arranged in the long form of the periodic table or the Modern Periodic Table?
Group 1 and 2 : s block : : group 13 and 18 : _______
The modern periodic table has 1 to 7 periods.
The modern periodic table shows the molecular masses of the elements in each frame.
p-block is composed of groups 1 and 2.
Write scientific reason.
Lithium and sodium are included in the same group in periodic table.
Distinguish between:
s-block - p-block
Noble gases belong to______ group of the periodic table.
The scientist who propounded the modern periodic law is ______.
Which of these belong to the same period?
| Element | A | B | C |
| Atomic number | 2 | 10 | 5 |
Which of the following statements about the Modern Periodic Table is correct:
Noble gases are placed in the ______ group in the modern periodic table.
An element has the atomic number 12.
- Write the electric configuration.
- To which group and period does it belong.
Explain the position of hydrogen in the periodic table.
A part of modern periodic table is given below. On its basis, answer the following questions:
| Group No. → | 1 | 2 | 13 | 14 | 15 | 16 | 17 | 18 |
| Period ↓ | ||||||||
| 2 | A | B | ||||||
| 3 | E | D | F | C |
Write the molecular formula of the compound formed by the combination:
A and F
Match the atomic number with the following:
An element of group 2.
