Bohr's Model Of The Atom
The present concept of atom was given by Neils Bohr. The Bohr's model of atom can be described as follows :
1.An atom is made up of three particles : electrons,protons and neutrons.Electrons have negative charge, protons have positive charge whereas neutrons have no charge, they are neutral. Due to the presence of equal number of negative electrons and positive protons, the atom on the whole is electrically neutral.
2.The protons and neutrons are located in a small nucleus at the centre of the atom.Due to the presence of protons, nucleus is positively charged.
3.The electrons revolve rapidly round the nucleus in fixed circular paths called energy levels or shells.The energy levels or shells are represented in two ways : either by the numbers 1, 2, 3, 4, 5and 6 or by the letters K, L, M, N, O and P (see Figure 21). The energy levels are counted from the centre outwards.
4.There is a limit to the number of electrons which each energy level (or shell) can hold, For example, the first energy level (or K shell) can hold a maximum of 2 electrons; second energy level (or L shell) can hold a maximum of 8 electrons; third energy level (or M shell) can hold a maximum of 18 electrons and fourth energy level (or N shell) can hold a maximum of 32 electrons.
5.Each energy level (or shell) is associated with a fixed amount of energy,the shell nearest to the nucleus having minimum energy and the shell farthest from the nucleus having the maximum energy.
6.There is no change in the energy of electrons as long as they keep revolving in the same energy level, and the atom remains stable.The change in the energy of an electron takes place only when it jumps from a lower energy level to a higher energy level or when it comes down from a higher energy level to a lower energy level. When an electron gains energy, it jumps from a lower energy level to a higher energy level,and when an electron comes down from a higher energy level to a lower energy level, it loses energy.
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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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4. 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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15. How to learn naming Chemical Formulae?
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16. All about Names of the Chemical Elements
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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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37. The Physical Properties of the Isotopes of an Element are Different
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40. 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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45. Valaence Electrons (Or Valancy Electrons)
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47. Reason for the Fractional Atomic Masses of Elements
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49. Relation Between Valency and Valence Electrons
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