Thomson's Model Of The Atom
When J.J. Thomson proposed his model of the atom in 1903,then only electrons and protons were known to be present in the atom. According to Thomson's model of the atom :
1.An atom consists of a sphere (or ball) of positive charge with negatively charged electrons embedded in it.
2.The positive and negative charges in an atom are equal in magnitude, due to which an atom is electrically neutral. It has no overall positive or negative charge.
Thomson's model of the atom is shown in Figure 7.The coloured area in the sphere (or ball) contains all the positive charge in the atom. The negatively charged electrons are spread throughout the positive charge. The total negative charge of electrons is equal to the total positive charge of the sphere. These equal and opposite charges balance each other due to which an atom becomes electrically neutral on the whole.
Thomson's model of the atom is similar to that of a chirstmas pudding.The electron embedded in a sphare of positive charge are like the currants (dry fruits) in a spherical chirstmas pudding.We can also compare Thomson's model of atom to a watermelon. The red,edible part of watermelon represents the sphere of positive charge whereas the black seeds embeded in watermelon are like electrons.Although Thomson's model of atom explained the electrically natural nature of atom but it could not explain the result of various experiments carried out by other scientists such as Ruthorford's experiment.
Before we describe Rutherford's experiment which led to the discovery of a gold.Alpha particle are much smaller than the gold atoms present in the gold foil.We will now describe Ruthordford's Experiment.
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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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3. For the symbols H, D and T,tabulate three sub-atomic particles found in each of them.
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5. Structure of The Atom - Study Points
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10. Arrangement Of Electrons In The Atoms
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12. Limitations of Rutherford's model of the atom
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16. All about Names of the Chemical Elements
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17. How to learn naming Chemical Formulae?
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21. Comparison between Proton, Neutron and Electron
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22. Electronic Configurations of First 20 Elements
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26. Rules for writing of distribution of electrons in various shells for the first 18 elements
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36. 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. Valaence Electrons (Or Valancy Electrons)
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45. Electronic Configurations of Noble Gases (or Inert Gases)
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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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