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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
How many rows and columns are there in the Modem Periodic Table?
Fill in the following blank with suitable word:
The basis for modern periodic table is ...............
Fill in the following blank with suitable word:
Group 18 elements are called ...............
Give two example of group 17 elements.
The atomic numbers of four elements P, Q, R and S are 6, 8, 14 and 16 respectively. Out of these, the element known as metalloid is:
(a) P
(b) Q
(c) R
(d) S
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.
Consider the following elements:
Na, Ca, Al, K, Mg, Li
Which of these elements belong to the same period of the periodic table?
Which element has the electronic configuration 2, 8, 2?
What is the number of valence electrons in the atoms of first elements in a period?
Explain why All the elements of a group have similar chemical properties.
Explain why All the elements of a period have different chemical properties.
State how the valency of elements varies in a group of the periodic table?
What is the usual number of valence electrons and valency of group 18 elements of the periodic table?
(b) What is the number of elements is 3rd period, the modern periodic table?
What are the groups in a periodic table? Give two characteristics of each.
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)
Consider the following elements:
20Ca, 8O, 18Ar, 16S, 4Be, 2He
Which of the above elements would you expect to be:
(i) very stable?
(ii) in group 2 of the periodic table?
(iii) in group 16 of the periodic table?
An element X belongs to 3rd period and group 2 of the periodic table. State:
(a) number of valence electrons
(b) valency
(c) metal or non-metal
(d) name of the element
How many groups and periods does the modern periodic table have?
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 barium has the atomic number 56. Look up its position in the periodic table and answer the following question.
Is it larger or smaller than caesium (Cs)?
The electronic configuration of an element T is 2, 8, 8, 1.
What is the period number of T?
What is the number of elements in the 1st period?
Give the symbol and valency of the following element and radical.
Potassium
How were elements arranged in the long form of the periodic table or the Modern Periodic Table?
The d-block elements are called as _______ elements.
Find the odd one out and give its explanation.
p-block is composed of groups 1 and 2.
Distinguish between:
Group 17 - Group 18
An element which is an essential constituent of all organic compounds belongs to
“Hydrogen occupies a unique position in Modern Periodic Table”. Justify the statement.
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?
Explain giving reason why although the nuclear charge in atoms increases in moving from left to right in a period as well as in moving from top to bottom in a group in the Modern periodic table, but the size of the atoms does not vary similarly in both situations.
State the group and period, of the element having three shells with three electrons in valence shell.
Match the atomic number with the following:
A rare gas.
Give reason for the following:
Inert gases do not form ion.
