Why can't bohr's model be used for multi electron atoms?
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Bohr’s model was an excellent feat at that time as it was the best possible explanation for the structure of an atom. But it failed on all multi-electron species. The following are his limitations.
Limitation of Bohrs’ Theory-
I. According to Bohr, the radiation results when an electron jumps from one energy orbit to another energy orbit, but how this radiation occurs is not explained by Bohr.
II. Bohrs theory has successfully explained the observed spectra for hydrogen atom and hydrogen like ions (e.g. He+, Li2+, Be3+ etc.), but it could not explain the line spectra of multi electron atoms.
III. Bohr’s model was two-dimensional where an atom is three-dimensional.
IV. He could not explain sophisticated spectroscopy techniques
V. He could not explain for Zeeman effect ( magnetic effect ) on the line spectra
VI. He is unable to explain of Stark effect ( electric Effect ) on the line spectra.
VII. In Bohr’s equation, the momentum and position of electron, revolving around the nucleus were well defined. But, according, Heisenberg’s Uncertainty principle, it is impossible to measure the position and momentum of electrons precisely. If the position is measure with maximum precision, there will be uncertainty in the value of momentum and vice versa.
VIII. Bohr treated electrons as particles but according to de Broglie’s hypothesis, having a very low mass, electron also exhibits wave nature.
IX. Acc. To Bohr the angular momentum (mvr) ofelectron in nth orbit is equal to nh/2π.But he is unable to give explanaition of this concept. (Later given by de Broglie).
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