CBSE Guess > Papers > Important Questions > Class IX > 2009 > Science > Science By : Mr M. p. Keshri
CBSE CLASS I X
Structure Of The Atoms (Solved)
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Q.117. The distribution of electrons, neutrons and protons are given below:
| Elements | Electrons | Neutrons | Protons |
| A | 4 | 4 | 3 |
| B | 8 | 9 | 9 |
| C | 18 | 22 | 18 |
| D | 17 | 20 | 17 |
| E | 17 | 18 | 17 |
From the above data find –
(i) a cation,
(ii) an anion,
(iii) atom of noble gas.
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Q. 118. What is meant by atomic number of an element ? What happens to the atomic number of an element when its atoms form ions ? Give example each of diatomic and triatomic molecules.
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Q. 119.Find the atomic number of an element which has 7 electrons in the M shell.
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Q. 120. The atomic number of chlorine is 17. Write the number of electrons in Cl-.
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Q. 121. There are 2 electrons in M shell of an element. Find the atomic number of the element.
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Q.122. Is there any change of atomic number when an element forms ions ?
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Q. 123. The atomic number of aluminium and chlorine are 13 and 17 respectively. Find the number of electrons present in Al+3 and Cl- respectively.
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Q. 124. Why certain atoms are radioactive while many others are not ?
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Q. 125. State the electronic configuration attained by chemically inert substances.
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Q. 126. If number of electrons in an atom is 8 and number of protons is also 8, then
(i )What is the atomic number of the atom ?
(ii) what is the charge on the atom ?
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Q. 127. Define isotope with suitable example.
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Q. 128. Two atoms A & B of chlorine have same nuclear charge. Mass number of A is 35 and mass number of B is 37. What are the atoms collectively called ? What is the difference between two ? Do they have same chemical properties ?
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Q. 129. Write the similar properties of isotopes.
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Q. 130. State the uses of isotopes.
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Q. 131. Atomic mass of an element is equal to the sum of number of protons and neutrons and is a whole number. How the fractional atomic masses of element is accounted ?
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Q. 132. Two atomic species A & B have the composition of their nuclei. Number of protons in both A & B are 6 while number of neutrons in A is 6 & in B is 8. State the relation between A & B and guess the elements which they represent.
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Q.133. Two atomic species X & Y have the composition of their nuclei. Number of protons in both X & Y are 8 while number of neutron in X is 8 and in Y is 10. State the relation between X & Y and guess the element they represent.
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Q. 134. A & B are two atoms whose nuclei contains protons and neutrons as under :
| Atoms | A |
B |
Number of protons |
6 |
6 |
Number of neutrons |
6 |
7 |
State the relationship between A & B and find the element they represent.
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Q.135. “Isotopes of an element differ in atomic masses and not in atomic number.” Comment.
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Q. 136. The number of electrons, protons and neutrons of species A, B, C, D, E are as under :
| Species | Electrons |
Protons |
Neutrons |
A |
4 |
6 |
6 |
B |
18 |
18 |
22 |
C |
17 |
17 |
20 |
D |
11 |
9 |
10 |
E |
17 |
17 |
18 |
Find from the table given above the species that represent :
(i) A cation
(ii) An anion
(iii) An atom of inert gas
(iv) A pair of isotopes.
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Q.137. The relative atomic mass of an element X is 16.2. Calculate the percentage of 16X8 and 18X8 isotopes in a sample of X.
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Q. 138. X, Y and Z are elements whose nuclei contains protons and neutrons as under :
| Atoms | Protons |
Neutrons |
X |
1 |
0 |
Y |
1 |
1 |
Z |
1 |
2 |
Name the elements and find their relations.
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Q. 139. Why isotopes of elements have the same chemical properties but different physical properties ?
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Q. 140. Define half-life.
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Paper By Mr. M. P. Keshari [ For Further Enquiry 09434150289]
