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| Modern Atomic Theory |
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| In view of new discoveries about atoms, Dalton's atomic theory was modified as given below: |
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 Atom is no longer indivisible as it has a complex structure of sub atomic particles (electrons, protons and neutrons). |
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 Atoms of the same element may posses different relative masses (isotopes). |
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 Certain atoms of different elements have same relative masses but their chemical properties are entirely different (isobars). |
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 Although the atom is composed of sub-atomic particles, it still is the smallest unit that takes part in a chemical reaction. |
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 The ratio in which the different atoms combine may be fixed and integral but may not always be simple. |
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 Atom of one element may be changed into atoms of another element (transmutation). |
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 The mass of an atom can be changed into energy (E = mc2) shows that atom is no longer indestructible. |
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