Chemistry

Structure of the Atom


Discovery of Neutron


After the discovery of protons and electrons,it was noticed that all the mass of an atom cannot be accounted for on the basis of only protons and electrons present in it. For example, a carbon atom contains 6 protons and 6 electrons.Now, the mass of electrons is so small that it can be ignored. So, the atomic mass of carbon should be only 6 u, which is the mass of 6 protons. This, however, is wrong because the actual atomic mass of carbon is 12 u. Then, how do we explain this extra mass of 6 units ? This problem was solved by the discovery of another subatomic particle by James Chadwick in 1932.This particle is called neutron.The neutron is a neutral particle found in the nucleus of an atom.Atoms of all the elements contain neutrons except ordinary hydrogen atom which does not contain any neutron.Thus, the subatomic particle not present in a hydrogen atom is neutron. A hydrogen atom contains only one proton and one electron. A neutron is represented by the symbol n.

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Notes


Structure of the Atom - Notes
1. Drawback of Rutherford’s Model of the Atom
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2. Rutherford’s Experiment - Discovery of Nucleus
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3. For the symbols H, D and T,tabulate three sub-atomic particles found in each of them.
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4. 4.Isotopes of Neon.
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5. Structure of The Atom - Study Points
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6. 3.Isotopes of Oxygen.
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7. Radioactive Isotopes
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8. Characteristics of a Neutron
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9. Nucleus
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10. Arrangement Of Electrons In The Atoms
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11. Characteristics of an Electron
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12. (b) Valency of Magnesium
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13. Limitations of Rutherford's model of the atom
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14. Mass Number
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15. All about Names of the Chemical Elements
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16. (d) Covalency of Nitrogen
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17. How to learn naming Chemical Formulae?
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18. 1. Isotopes of Hydrogen.
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19. Characteristics of a Proton
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20. Comparison between Proton, Neutron and Electron
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21. Electronic Configurations of First 20 Elements
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22. Thomson's Model Of The Atom
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23. Discovery of Neutron
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24. (e) Valency of Oxygen
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25. (d) Valency of Chlorine
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26. Rules for writing of distribution of electrons in various shells for the first 18 elements
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27. Isotopes
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28. 2.Covalency
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29. (a) Covalency of Hydrogen
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30. Covalency of Oxygen
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31. Bohr's Model Of The Atom
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32. Rutherford's Model Of The Atom
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33. 2.Isotopes of Carbon.
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34. Discovery Of Electron
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35. The Physical Properties of the Isotopes of an Element are Different
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36. Atomic Number
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37. Charged Particles in Matter
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38. (a) Valency of Sodium
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39. All the Isotopes of an Element Have Identical Chemical Properties
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40. Discovery of Proton
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41. Valaency Of Elements
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42. Relationship Between Mass Number and Atomic Number
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43. (f) Valency of Nitrogen
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44. Valaence Electrons (Or Valancy Electrons)
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45. Electronic Configurations of Noble Gases (or Inert Gases)
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46. Covalency of Chlorine
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47. Cause of Chemical Combination
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48. Reason for the Fractional Atomic Masses of Elements
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49. Applications of Radioactive Isotopes
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50. Relation Between Valency and Valence Electrons
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