Bohr! (1 Viewer)

[Ashlee88]

I was wondering if anybody could please help me on a couple of questions. I have read so many texts and web pages but can not find anything that is what I am after.

Explain how Bohr was able to modify Rutherfords model.

Outline the advances to nuclear science due to the contributions of Heinsberg and Pauli.

 

[rama_v]

I was wondering if anybody could please help me on a couple of questions. I have read so many texts and web pages but can not find anything that is what I am after.

Explain how Bohr was able to modify Rutherfords model.

Outline the advances to nuclear science due to the contributions of Heinsberg and Pauli.

(1) Bohr introduced the idea of quantised energy levels for electrons, he said that electrons which orbitted in the ground state did not emit emr (unlike Rutherford's model where the electron was constantly emitting emr as it underwent centripetal acceleration around the nucleus), and he also said that angular momentum was quantised. You can prove the last one by usign deborglie's formula L=h/mv where L is lambda (wavelength)
The maths behind Bohr's last postulate (that angular momentum was quantised):
nL=2pi r (2*pi*r is the circumference while nL is integral number of wavelengths, they must equal if Bohr's postulates are true)
nh/mv = 2 pi r
.:nh/2pi = mvr

and since mvr = angular momentum, it must mean that angular momentum is quantised, i.e. must take integral values of nh/2pi.

Finally you shold also mention that Bohr said that when an electron jumped from a higher energy shell to a lower energy shell it emitted emr with a frequency given by Planck's equation E=hf.

(2) Both Heisenberg and Pauli had a huge impact on our understanding of atoms..I would talk about how Heisenbergs uncertaintly principle changed the direction of quantum physics away from exact values and into an era of chance and probability. Pauli contributed through his exclusion principle by stating that no two electrons could share the 4 same quantum numbers (you can read in a textbook what these 4 quantum numbers represent)...This explained the arrangement of electrons in energy shells in atoms, and it may surprise you to know that this is what the modern periodic table is built upon. Thus we owe the structure of the periodic table as it is today to Pauli's work.

 

[who_loves_maths]

^ i think Ashlee88 was asking about Heisenberg and Pauli's contributions to nuclear science - not the general Atomic Theory...


Ashlee, nuclear science is a discipline dealing with the properties of the nuclei of atoms; here's how Heisenberg's Uncertainty Principle, and Pauli's proposition of the existence of the neutrino contributed to nuclear science:

1) for the Uncertainty Principle - it explained the possibility of alpha decay within an unstable nucleus. The principle provided an explanation for why some of the alpha particles ejected from the nucleus of an atom had less kinetic energy than that is usually required in order for a particle of similar size to escape the attractive forces of the nucleus {related also to mass defect and binding energy of the nucleus}.
the Principle provided the resolution that since the position of any quantum particles cannot be exactly known, then the probabilistic 'picture' of the atom means that an alpha particle has a distinct probability of being actually physically outside the nucleus of the atom at any moment in time.
so in essence, the alpha particle, in this way, is allowed to 'dig' out of the nucleus with less kinetic energy than is predicted by Classical theory... this is a process called quantum tunnelling and governs many of the nuclear processes studied in nuclear science.


2) for Pauli's neutrino - it explained the "missing energy" of the beta decay of nucleons within an atom, thereby also confirming the validity of the Law of Conservation of Energy and Mass at the atomic level. Pauli's contribution here was the provision of a theoretical explanation which accounted for the 'lost' energy in beta decays where either a proton or a neutron decays into each other respectively... the proposed massless particle, the neutrino, was responsible for carrying away this 'lost energy'.
the detection of the neutrino later on was experimental proof for Pauli's proposition.
his contribution ultimately led to a broader understanding of the processes of beta decay in nuclear interations and opened up the study into the possible existence of more, but then undiscovered, sub-atomic particles in the 1930s and onwards...


hope this helps answer your second question Ashlee

 

[rama_v]

^ i think Ashlee88 was asking about Heisenberg and Pauli's contributions to nuclear science - not the general Atomic Theory...


Ashlee, nuclear science is a discipline dealing with the properties of the nuclei of atoms; here's how Heisenberg's Uncertainty Principle, and Pauli's proposition of the existence of the neutrino contributed to nuclear science:

1) for the Uncertainty Principle - it explained the possibility of alpha decay within an unstable nucleus. The principle provided an explanation for why some of the alpha particles ejected from the nucleus of an atom had less kinetic energy than that is usually required in order for a particle of similar size to escape the attractive forces of the nucleus {related also to mass defect and binding energy of the nucleus}.
the Principle provided the resolution that since the position of any quantum particles cannot be exactly known, then the probabilistic 'picture' of the atom means that an alpha particle has a distinct probability of being actually physically outside the nucleus of the atom at any moment in time.
so in essence, the alpha particle, in this way, is allowed to 'dig' out of the nucleus with less kinetic energy than is predicted by Classical theory... this is a process called quantum tunnelling and governs many of the nuclear processes studied in nuclear science.


2) for Pauli's neutrino - it explained the "missing energy" of the beta decay of nucleons within an atom, thereby also confirming the validity of the Law of Conservation of Energy and Mass at the atomic level. Pauli's contribution here was the provision of a theoretical explanation which accounted for the 'lost' energy in beta decays where either a proton or a neutron decays into each other respectively... the proposed massless particle, the neutrino, was responsible for carrying away this 'lost energy'.
the detection of the neutrino later on was experimental proof for Pauli's proposition.
his contribution ultimately led to a broader understanding of the processes of beta decay in nuclear interations and opened up the study into the possible existence of more, but then undiscovered, sub-atomic particles in the 1930s and onwards...


hope this helps answer your second question Ashlee

oh, lol sorry, we havent yet covered that part of the sylabus, I thought she was referring to the atomic model lol. my fault..