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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
The position of three elements A, B and C in the Periodic Table are shown below –
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Group 16
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Group 17
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A
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−
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B
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C
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(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
What is the significance of atomic number in the modern classification of elements? Explain with the help of an example.
Would you place the two isotopes of chlorine, CI-35 and CI-37 in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.
Name the scientist who prepared modern periodic table.
Which of the following statement about the modern periodic table is correct?
(a) It has 18 horizontal rows known as periods.
(b) It has 7 vertical columns known as periods.
(c) It has 18 vertical columns known as groups.
(d) It has 7 horizontal rows known as groups.
Give alongside is a part of the periodic table :
As we move horizontally from left to right:
| Li | Be | B | C | N | O | F | |
| Na | Mg | Al | Si | P | S | Cl |
(i) What happens to the metallic character of the elements?
(ii) What happens to the atomic size?
How would the tendency to gain electrons change on moving from left to right in a period 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?
State how the valency of elements varies in a group of the periodic table?
Explain why, the first period of the periodic table has only two elements whereas second period has eight elements
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)
Name two elements in halogens.
Name two elements in each case: Lanthanides
What do you understand by typical elements?
Name the type of elements which have outermost shell incomplete.
Answer the following in respect of element `31/15 P`
Give its electronic configuration
An element barium has atomic number 56. Look up its position in the periodic table and answer the following question.
What will be the formula of its phosphate?
An element E has following electronic configuration:
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K |
L |
M |
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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.
How will the tendency to gain electrons change as we go from left to right across a period? Why?
What would be the correct order if Zn, Fe, Al and Cu are arranged in increasing order of reactivity?
What is the number of elements in the 1st period?
Give the symbol and valency of the following element and radical.
Potassium
Give the symbol and valency of the following element and radical.
Hydrogen
Give the symbol and valency of the following element and radical.
Aluminium
How were elements arranged in the long form of the periodic table or the Modern Periodic Table?
Right or wrong sentence.
The modern periodic table shows the molecular masses of the elements in each frame.
Complete the following flow chart.
Explain structure of modern periodic table in short.
Elements in the modern periodic table are arranged in ______groups and______ periods.
Identify gas A in the following experiment.
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?
If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?
Noble gases are placed in the ______ group in the modern periodic table.
Define groups of modern periodic table.
Name two elements that you would expect to show chemical reactions similar to calcium. What is the basis of your choice?
Name the following metal:
A metal present in period 3, group 1 of the periodic table.
Match the atomic number with the following:
An element of group 2.
