Why is Bohr's model of an atom limited to explaining only the hydrogen spectrum?

In summary, Bohr's model of the atom is not able to explain the spectrum of atoms other than hydrogen because it only accounts for a single electron and does not take into account relativistic effects for heavier atoms. Although it can provide an approximation for light atoms, it does not work well for heavy atoms. Additionally, the concept of orbital speed is not applicable to electrons, but is used in the Bohr model to explain the behavior of hydrogen atoms.
  • #1
kay
60
2
Why is Bohr's model of an atom not able to explain the spectrum of atoms other than hydrogen? Can you give an example? :what:
 
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  • #2
Is that homework?

Here is a hint: other atoms have more than one electron. Is this taken into account in the Bohr model?
 
  • #3
No, it isn't. While reading the chapter i encountered this line which says that Bohr's model can't explain the spectrum of atoms other than hydrogen.
But another doubt, can Bohr's model explain the spectrum of species isoelectronic to Hydrogen?
 
  • #4
The Bohr model gives a reasonable approximation for light atoms (not molecules!) with just a single electron, yes.
It does not work well for heavy atoms due to relativistic effects and the size of their nuclei.
 
  • #5
Relativistic effects? :/
 
  • #6
Imagine a uranium nucleus with one electron, i.e. a U91+ ion. Calculate the orbital speed in the first Bohr orbit, assuming non-relativistic mechanics.
 
  • #7
I'm a student of 11th class. I have no idea. I don't even know orbitals had speed.
I don't know what is relativistic or anything. Sorry. I can't understand anything. :(
 
  • #8
Sorry, I thought you had at least seen a derivation of the Bohr orbit radii, which includes the orbital speed along the way. If you haven't, try the Wikipedia article on the Bohr model. It has enough information that you should be able to get the electron speed in orbit "n" with only a little bit of algebra.

The boundary between "non-relativistic" and "relativistic" is not sharp, but a common rule of thumb is that if a speed is greater than 0.1c, you really should be using relativistic equations.
 
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  • #9
kay said:
I don't even know orbitals had speed.
They do not, but Bohr's orbits have a speed.

If that speed gets comparable to the speed of light ("c"), the formulas from classical mechanics (like kinetic energy = ##\frac{1}{2}m v^2##) get imprecise to outright wrong and you have to consider special relativity.
 
  • #10
You should first do study of different quantum numbers assigned to electrons in an atom,Bohrs theory was succesfu l in expaining hydrogen spectra at that time,but it was a rudimentary theory made out of Plancks law and observation of hydrogen spectra.
 

Related to Why is Bohr's model of an atom limited to explaining only the hydrogen spectrum?

What is Bohr's model of an atom?

Bohr's model of an atom is a theoretical model proposed by Niels Bohr in 1913, which describes the structure of an atom as a positively charged nucleus surrounded by negatively charged electrons that orbit the nucleus in fixed energy levels.

What are the main features of Bohr's model?

The main features of Bohr's model include the concept of discrete energy levels, in which electrons can only exist in specific energy states and can jump between energy levels by absorbing or emitting photons. It also introduced the idea of a central nucleus containing protons and neutrons, with the number of protons determining the element's identity.

How is Bohr's model different from previous atomic models?

Bohr's model is different from previous atomic models in that it incorporates the concept of quantized energy levels, which was not included in earlier models such as the Thomson and Rutherford models. It also explains the stability of atoms by proposing that electrons can only exist in specific orbits or energy levels, rather than being able to move freely around the nucleus.

What are the limitations of Bohr's model?

Bohr's model has several limitations, including its inability to accurately predict the behavior of atoms with more than one electron. It also does not account for the wave-like behavior of electrons, which is better described by quantum mechanics. Additionally, it does not explain the existence of subatomic particles such as neutrons and does not account for the concept of electron spin.

How does Bohr's model contribute to our understanding of the atom?

Bohr's model was a significant contribution to our understanding of the atom, as it provided a better explanation for the stability of atoms and the spectral lines observed in the emission and absorption of light. It also paved the way for further developments in atomic theory, leading to the development of quantum mechanics and a deeper understanding of the behavior of subatomic particles.

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