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प्रश्न
Write a short note.
Position of isotopes in the Mendeleev’s and the modern periodic table.
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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
What is periodicity in properties of elements with reference to the Modern Periodic Table?
How does the tendency of elements to gain electrons change as we move from left to right in a period? State the reason of this change.
What is the name of those elements which divide metals and non-metals in the periodic table?
Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?
The modern periodic table was prepared by ______.
Consider the following elements:
Na, Ca, Al, K, Mg, Li
Which of these elements belong to the same group of the periodic table?
How would the tendency to lose electrons change as we go from left to right across a period of the periodic table?
What is the usual number of valence electrons in the atoms of the last element in a period?
State whether the following statement is true or false:
On going down in a group of the periodic table, the number of valence electrons increases.
What is the major characteristic of the first elements in the periods of the periodic table? What is the general name of such elements?
What is the fundamental difference in the electron configurations between the group 1 and group 2 elements?
What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?
What is the number of elements is 1st period the modern periodic table?
Name the scientist who stated the modern periodic law.
Correct the statement.
Transition elements are placed at extreme right of the periodic table.
Name the type of elements which have outermost shell complete.
State its position in the periodic table?
An element E has following electronic configuration:
|
K |
L |
M |
|
2 |
8 |
6 |
(a) To which group of the periodic table does element E belong?
(b) To which period of the periodic table does element E belong?
(c) State the number of valence electrons present in element E.
(d) State the valency of the element E.
What would be the correct order if Zn, Fe, Al and Cu are arranged in increasing order of reactivity?
An element A has 2 electrons in its fourth shell. State its electronic configuration.
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- Number of electrons in their atoms
- Their tendency to lose electrons
- Their metallic characters
- Formation of their oxides
- Formulae of their chlorides
Give the symbol and valency of the following element and radical.
Sodium
Give the symbol and valency of the following element and radical.
Bicarbonate
Give the symbol and valency of the following element and radical.
Bisulphite
Give the symbol and valency of the following element and radical.
Sulphate
Give the chemical formula of sodium bicarbonate
What are the periods in a periodic table?
The groups 1 and 2 constitute the _______ block.
Which of the following statements about the Modern periodic table is correct?
Explain structure of modern periodic table in short.
What are groups and periods in the modern periodic table?
______ and ______ are called inner transition elements.
The amount of energy released when one or more electrons is added to the neutral atom is ______
The longest period of the Modern Periodic Table is period.
What is the symbol of the element Tungsten?
Spot the error:
There are 5 periods and 17 groups in the modern periodic table.
Name the following metal:
A metal present in period 3, group 1 of the periodic table.
