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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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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4. For the symbols H, D and T,tabulate three sub-atomic particles found in each of them.
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9. Structure of The Atom - Study Points
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10. Limitations of Rutherford's model of the atom
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11. Arrangement Of Electrons In The Atoms
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12. All about Names of the Chemical Elements
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17. How to learn naming Chemical Formulae?
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22. Rules for writing of distribution of electrons in various shells for the first 18 elements
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24. Electronic Configurations of First 20 Elements
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25. Comparison between Proton, Neutron and Electron
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33. The Physical Properties of the Isotopes of an Element are Different
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39. All the Isotopes of an Element Have Identical Chemical Properties
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42. Relationship Between Mass Number and Atomic Number
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44. Electronic Configurations of Noble Gases (or Inert Gases)
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50. Applications of Radioactive Isotopes
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