Atom
We all are too curious to know about the smallest unit of
matter which result in invention of discoveries with some scientist like
Dalton, Thomson, Rutherford and then era of discoveries towards elementary
particle started.
Bohr gives drastic concept and mathematical explanation for
atom structure works as planetary system after that Sommerfeld and Zeeman came
with correction in atomic theory then Schrodinger shows some new way that
change the full concept of atom structure.
basic starting model : development-of-the-atomic-model
Let’s rid starting basic model with direct jump on Bohr’s model.
Bohr assumption based on Hydrogen atom.
BOHR'S MODEL
BOHR'S MODEL
BOHR'S COMES WITH THREE
POSTULATES
- · The electron moves in circular orbits around the proton under the influence of the electric force of attraction
- · Only certain electron orbits are stable. When in one of these stationary states, as Bohr called them, the electron does not emit energy in the form of radiation. Hence, the total energy of the atom remains constant and classical mechanics can be used to describe the electron’s motion.
- · The atom emits radiation when the electron makes a transition from a more energetic initial orbit to a lower-energy orbit. This transition cannot be visualized or treated classically.
- The size of an allowed electron orbit is determined by a condition imposed on the electron’s orbital angular momentum: the allowed orbits are those for which the electron’s orbital angular momentum about the nucleus is quantized and equal to an integral multiple of mvr =nh/2pi
** Physics In Deep**
‘The question arise here “how
the Bohr knew about the quantization of angular momentum”.
I think he thought about the standing wave of atom and it can only occur in harmonica OR he found it in practical experiment at that time.
I think he thought about the standing wave of atom and it can only occur in harmonica OR he found it in practical experiment at that time.
It is easy to show Bohr's
quantization of angular momentum.
Bohr’s theory fail due to
following limitation of his theory
the value of speed of electron is more than light it is not possible so we can say electron not exist inside the nucleus .
- It can explain the spectrum of one electron atom or H like atom
- It not explain Zeeman effect and stark effect
- It violate Heisenberg uncertainty principle
- It fails to give any information regarding the distribution and arrangement of electrons in atoms.
- · It fails to explain the transitions of electrons from one level to another, the rate at which they or the selection rules which apply to them
- · It was found that when electric or magnetic field is applied to the atom, each spectral line is splitted into several lines. The former one is called Stark effect while the later as Zeeman Effect. Bohr’s theory fails to explain these effects.
Before going to next get some basic topic and
important topics to learn more
Photoelectric effect: http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Quantum_Mechanics/01._Waves_and_Particles/Case_Study%3A_Photoelectric_Effect
Hesinberg uncertainty principle: http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Quantum_Mechanics/09._The_Hydrogen_Atom/Atomic_Theory/Electrons_in_Atoms/Uncertainty_Principle
These are basic topics
But here im discuss some deep concept
**
physics in deep **
# Why electron not exists in side nucleus ?
we know
we know
Mass of electron, m = 9.1 x 10-31 kg, Dx or size of nucleus =1 x 10-15 m.
the value of speed of electron is more than light it is not possible so we can say electron not exist inside the nucleus .
H
spectrum
Basically Bohr's theory is not comes from H
spectrum but is gives very fine define of H spectrum
**Physics
in deep**
The explanation of Bohr is not fail but he
not conclude about the discontinuous spectrum line and about the variation of
its intensities
Then sommerfeld come with correction in Bohr's
model
He say Bohr's circular orbit is case of special ellipse
***PHYSICS IN DEEP ***
Sommerfeld model
when sommerfeld repeat the experiment of H spectrum he find the explanation of Bohr's spectrum line is seem to wrong he find the bohr's the line comes from 2nd orbit to 1st orbit is 2 single line and from 3rd to 1st orbit transition contains 3 lines similarly from 4th to 1st transition contains 4 lines and so on under the high resolution microscope but bohr observe single spectrum line for each so sommer feld conclude that the orbit consist sub orbit and these are elliptical
***PHYSICS IN DEEP ***
Sommerfeld model
when sommerfeld repeat the experiment of H spectrum he find the explanation of Bohr's spectrum line is seem to wrong he find the bohr's the line comes from 2nd orbit to 1st orbit is 2 single line and from 3rd to 1st orbit transition contains 3 lines similarly from 4th to 1st transition contains 4 lines and so on under the high resolution microscope but bohr observe single spectrum line for each so sommer feld conclude that the orbit consist sub orbit and these are elliptical
**PHYSICS IN DEEP **
Zeeman effect
Zeeman effect
The zeeman is next test the bhor theory but he applied magnetic to atom and check out its spectrum he found that there is more lines present in sommerfeld model each line further more divided like sommer feld p lines is now three lines
When he tried to conceptualize the practical result he concluded that there are orbitals in sub orbits and these are basically the orientation of path or electron into its sub orbit
Key point
Why he got more lines he say when expernal feild intract with electron magnetic feild then it requires energy to align in the direction of external feild and different orientation of electron path it requires different amount of energy soo number of lines is diffrent orientation of electron path
***My next post is related to basics of quantum mechanics and in deep of that****
