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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
Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the Periodic Table. Write the electronic configuration of these two elements. Which of these will be more electronegative? Why?
Write the names given to the vertical columns and horizontal rows in the Modern Periodic Table. How does the metallic character of elements vary on moving down a vertical column? How does the size of atomic radius vary on moving left to right in a horizontal row? Give reason in support of your answer in the above two cases.
Fill in the following blank with suitable word:
Group 1 elements are called ...............
How many periods and groups are there in the long form of periodic table?
where should hydrogen be placed in the modern periodic table? Give reason for your answer.
Is it possible to have an element having atomic number 1.5 placed between hydrogen and helium?
Which element has the electronic configuration 2, 8, 2?
How would the tendency to gain electrons change on moving from left to right in a period of the periodic table?
How does the chemical reactivity of the halogens vary on going in group 17 of the periodic table?
What is the number of valence electrons in the atoms of first elements in a period?
What is the usual number of valence electrons in the atoms of the last element in a period?
State how the valency of elements varies in a group of the periodic table?
On the basis of electronic configuration, how will you identify the first element of a period?
What are the merits of the modern periodic table of elements?
In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group.
State the term
The tabular arrangement of elements in horizontal rows and vertical columns _________
Name the scientist who stated the modern periodic law.
Name two elements in halogens.
Name two elements in each case:
Transition element
Answer the following in respect of element `31/15 P `
To which group and period does it belong?
Fill in the blank:
The horizontal rows in the periodic table are called _____________.
Write a short note.
Structure of the modern periodic table.
What is the number of elements in the 1st period?
Name an element of group 18 which can form compounds.
Give the symbol and valency of the following element and radical.
Nitrogen [Nitride]
Give the symbol and valency of the following element and radical.
Bicarbonate
State any five features of modern periodic table.
______ and ______ are called inner transition elements.
Identify gas A in the following experiment.
Element ‘X’ forms a chloride with the formula XCl2, which is solid with a high melting point. X would most likely be in the same group of the periodic table as: ______
The amount of energy released when one or more electrons is added to the neutral atom is ______
The inert gas which lies in the third period is ______
The element with atomic number 14 is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?
The maximum number of electrons that can be accommodated in s, p,d, and f subshells are ______.
An element with atomic number ______ will form a basic oxide.
Name the following metal:
A metal present in period 3, group 1 of the periodic table.
An element has 2 electrons in its N shell.
State its position in periodic table.
