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. 141. Carbon-14 is radioactive but carbon-12 not. Comment.
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Q. 142. A radioisotope has a half-life of 900 seconds. What fraction of original isotope would remain behind after five half-life periods.
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Q. 143. The half-life period of actinium is 15 seconds. Suppose 10 mg of actinium is kept. How much would be left at the end of 45 seconds ?
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Q. 144. What is radioisotope dating ?
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Q. 145. A sample has only 25% as much carbon-14 as in a living sample. If half-life of C-14 is 5800 years, calculate the age of the sample.
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Q. 146. Sulphur has four naturally occurring isotopes with mass numbers 32, 33, 34, 35 and atomic number 16.
(i) Write atomic symbol for each indicating mass number and atomic number.
(ii) Would these have similar physical or chemical properties ?
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Q. 147. There are two radioactive substances A & B, atoms of A disintegrate faster than those of B. Which has short half-life period ? Which has longer ?
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Q. 148. What do you understand by nucleons ?
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Q. 149. What can we say about physical and chemical properties of isobars ?
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Q. 150. Describe the experimental process that led to the discovery of isotopes.
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Q. 151. For the symbol H, D and T tabulate three sub-atomic particles found in each of them.
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Q. 152. Write the electronic configuration of any one pair of isotopes and isobars.
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Q. 153. Compare the properties of electrons, protons and neutrons.
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Q. 154. What are the limitations of J. J. Thomson’s model of the atom ?
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Q. 155. What are the limitations of Rutherford’s model of the atom ?
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Q.156. Describe Bohr’s model of the atom.
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Q. 157. Compare all the proposed model of an atom.
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Q. 158. Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.
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Q. 159. Define valency by taking examples of silicon and oxygen.
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Q. 160. Explain with examples,
(i) Atomic number,
(ii) Mass number,
(iii) Isotopes and
(iv) Isobars. Give any two uses of isotopes.
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Q. 161. Na+ has completely filled K and L shells. Explain.
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Q. 162. If bromine atom is available in the form of, say, two isotopes 79Br35 (49.7%) and 81Br35 (50.3%), calculate the average atomic mass of bromine atom.
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Q. 163. If Z = 3, what would be the valency of the element ? Also, name the element.
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Q. 164. Complete the following table :
Atomic Number |
Mass Number |
Number of neutrons |
Number of protons |
Number of electrons |
Name of the atomic species |
9 |
--- |
10 |
--- |
--- |
--- |
16 |
32 |
--- |
--- |
--- |
Sulphur |
--- |
24 |
--- |
12 |
--- |
--- |
--- |
2 |
--- |
1 |
--- |
--- |
--- |
1 |
0 |
1 |
0 |
--- |
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Paper By Mr. M. P. Keshari [ For Further Enquiry 09434150289]
