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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
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium?
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(a) P
(b) Q
(c) R
(d) S
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Ca, Cl, Na, I, Li, Ba, Sr, K, Br
Separate these elements into three groups (families) of similar properties. State one property in each case on the basis of which you have made your choice.
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What is the usual number of valence electrons and valency of group 18 elements of the periodic table?
What is a group in the periodic table?
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Which of the following are the correct characteristics of isotopes of an element?
(i) same atomic mass
(ii) same atomic number
(iii) same physical properties
(iv) same chemical properties
(a) (i), (ii) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
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Name the type of elements which have outermost shell complete.
Name the type of elements which have outermost shell incomplete.
Name the type of elements which have two electrons in the outermost orbit.
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Third Period.
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Give the symbol and valency of the following element and radical.
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Give the symbol and valency of the following element and radical.
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Give the symbol and valency of the following element and radical.
Bisulphate
Give the symbol and valency of the following element and radical.
Sulphate
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Fill in the blank:
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Find the odd one out and give its explanation.
Find the odd one out and give its explanation.
Write an explanation.
Period
______ and ______ are called inner transition elements.
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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 |
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State the group and period, of the element having three shells with three electrons in valence shell.
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Boron, Aluminium, Gallium, Indium, Thallium
Answer the following question in relation to the above group of elements:
If the electronic configuration of aluminium is 2, 8, 3, how many electrons are there in the outer shell of thallium?
