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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?
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Name the scientist who first of all showed that atomic number of an element is a more fundamental property than its atomic mass.
Fill in the following blank with suitable word:
Group 17 elements are known as ...............
Fill in the following blank with suitable word:
Group 18 elements are called ...............
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The three elements having chemical symbols of Si, B and Ge are:
(a) all metals
(b) all non-metals
(c) all metalloids
(d) Si is metalloid, B is metal and Ge is non-metal
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 a period in a periodic table?
What are the merits of the modern periodic table of elements?
What are the periods in a periodic table? Give two characteristics of each.
Correct the statement.
Transition elements are placed at extreme right of the periodic table.
Name two elements in Alkaline earth metals.
Name two elements in halogens.
Answer the following in respect of element `31/15 P `
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Answer the following in respect of element `31/15 P`
Give its electronic configuration
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What is the period number of T?
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- Number of electrons in their atoms
- Their tendency to lose electrons
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- Formation of their oxides
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Name the cation and the anion in the salt – calcium sulphate
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Give the symbol and valency of the following element and radical.
Hydroxide
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Group 1 and 2 : s block : : group 13 and 18 : ______
Write a scientific reason.
There was ambiguity about the correct position of hydrogen in Mendeleev’s periodic table.
Position of A, B and C three elements is given in the table from the modern periodic table. Answer the following questions.
| Periods | Group 2 | Group 17 |
| 2 | ----- | A |
| 3 | B | ----- |
| 4 | ----- | C |
- What is an element metal or nonmetal?
- Which is the outermost orbit of element B?
- Identify C element and it's physical state.
Explain structure of modern periodic table in short.
What are groups and periods in the modern periodic table?
State any five features of modern periodic table.
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The inert gas which lies in the third period is ______
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The three elements A, B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.
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 |
Which of the element is a Noble gas?
- Write the electronic configuration of element X, given by its symbol as under: \[\ce{^40_20 X}\]
- Determine its position in the modem periodic table.
- What is the nature of its oxide?
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Define groups of modern periodic table.
Match the atomic number with the following:
A rare gas.
