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Atomic Structure and Chemical Bonding — CHEMISTRY STD 9 — Question

ICSE BoardEnglish MediumSTD 9CHEMISTRYAtomic Structure and Chemical Bonding5 Marks
Question
How does the Modern atomic theory contradict and correlate with Dalton's atomic theory?
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Answer

The latest research on the atom has proved that most of the postulates of Dalton's atomic theory contradict. However, Dalton was right that atoms take part in chemical reactions. Comparisons of Dalton's atomic theory with the modern atomic theory. Dalton's atomic theory:
  1. Atoms are indivisible.
  2. Atoms of the same element are similar in every respect.
  3. Atoms combine in a simple whole-number ratio to form molecules.
  4. Atoms of different elements are different.
  5. Atoms can neither be created nor be destroyed.
Modern atomic theory:
  1. Atoms are no longer indivisible and consist of electrons, protons, neutrons and even more sub-particles.
  2. Atoms can be changed in energy.
  3. Atoms of the same element may differ from one another called isotopes. i.e.$ ^{12}_6C ^{13}_6C ^4_6C.$
  4. Atoms of different elements may be similar called isobars.
  5. Atoms combine in a ratio which is not a simple whole-number ratio; e.g. in sugar, the $C_{12}H_{22}O_{11}$​​​​​​​ ratio is not a whole number ratio.

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