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. 90. What are valence electrons ? Explain with examples.
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Q. 91. State the electron which decide the chemical properties of the element.
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Q. 92. Define valency of an atom.
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Q. 93. Find the number of electrons present in K, L and M shell of an element having 16 protons. What will its electrovalency be ?
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Q. 94. Helium, Neon and Argon has 0 (zero) valency. Comment.
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Q. 95. State the electronic configuration of sulphur, nitrogen and beryllium. Also write their valencies.
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Q. 96. How will you find the valency of chlorine, sulphur and magnesium.
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Q. 97. What is atomic number ? How the definition of an element is improved by this concept ?
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Q. 98. How atomic number is the fundamental property of an element ?
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Q. 99. Define atomic number and mass number of an atom in an element.
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Q. 100. Atomic nucleus of an element has mass number equal to 23 and neutron number equal to 12. Calculate its atomic number. State the symbol of the element.
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Q. 101. The mass number of an element is 18. It has 7 electrons. Find the number of protons and neutrons. What is the atomic number of the element ?
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Q. 102. How will you write the electronic configuration of the atom of an element whose mass number is 35 and atomic number is 16. Write the number of electrons, protons and neutrons.
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Q. 103. Atomic mass of an element is 39 and atomic number is 19. Find the number of electrons and write its electric configuration.
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Q. 104. Potassium has 19 electrons and its electronic configuration is as K = 2, L = 8, M = 8, N = 1. Why cannot we put 9 electrons in M-shell as it can accommodate at most 18 electrons ?
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Q. 105. The atomic number of an element X is 12, write its atomic configuration.
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Q. 106. Atomic weight of an element X is 24 and its atomic number is 12, how many neutrons does its atom have ? How many electrons are there in K, L, and M shells of its atom ?
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Q. 107. Why atom is an electrically neutral particle ?
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Q. 108. Illustrate with example, how will you find the atomic mass of an element ?
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Q. 109. Atomic number of an element is 15. Write its electronic configuration and indicate the number of shell it will occupy.
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Q. 110. Electron of an atom occupies three shells. What do you mean by this? Is it possible that the same atom of an element may have more shells ?
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Q. 111. Complete the following table :
| Element | Atomic number | Protons | Electrons | Neutrons | Mass number |
| A | 17 | -- | -- | 18 | -- |
| B | -- | -- | 14 | 14 | -- |
| C | -- | 9 | -- | -- | 19 |
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Q. 112. Atomic numbers and atomic mass numbers of some elements are given below. Complete the following table :
| Elements | Atomic number | Mass number | Protons | Neutrons | Electronic config. |
| A | 14 | 28 | -- | -- | --- |
| B | 18 | 40 | -- | -- | --- |
| C | 11 | 23 | -- | -- | --- |
| D | 17 | 35 | -- | -- | --- |
| E | 20 | 40 | -- | -- | --- |
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Q. 113. The mass number of chlorine is 35 and its atomic number is 17. How the chlorine atom will be represented ?
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Q. 114. Write the mass number and atomic number in the following elements representation :
16O8
32S16
23Na11
31P15.
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Q. 115. How does an atom become a cation ?
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Q. 116. What is an anion ?
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Paper By Mr. M. P. Keshari [ For Further Enquiry 09434150289]
