Comments on: The Bohr Atom http://www.talkingscience.org/2009/04/the-bohr-atom/ TalkingScience is a non-profit organization focus on educating the general public on science through new media. Tue, 07 Feb 2012 01:53:00 +0000 hourly 1 http://wordpress.org/?v=abc By: Jessica_2012 http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-103027 Jessica_2012 Fri, 13 Jan 2012 05:51:00 +0000 http://talkingscience.org/blogs/?p=1696#comment-103027 Hello all, The Bohr Model is probably familar as the "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy (a bit of a misnomer, since the energy in "atomic energy" is actually the energy of the nucleus, rather than the entire atom). In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun (but the orbits are not confined to a plane as is approximately true in the Solar System). The adjacent image is not to scale since in the realistic case the radius of the nucleus is about 100,000 times smaller than the radius of the entire atom, and as far as we can tell electrons are point particles without a physical extent. The most common form of commercial T-shirt decoration is screen-printing that can be obtained by <a href="http://www.pandinavia.ch" rel="nofollow">werbemittel</a> or alike store or market point. In screen-printing, a design is separated into individual colors. Hello all,
The Bohr Model is probably familar as the "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy (a bit of a misnomer, since the energy in "atomic energy" is actually the energy of the nucleus, rather than the entire atom). In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun (but the orbits are not confined to a plane as is approximately true in the Solar System). The adjacent image is not to scale since in the realistic case the radius of the nucleus is about 100,000 times smaller than the radius of the entire atom, and as far as we can tell electrons are point particles without a physical extent. The most common form of commercial T-shirt decoration is screen-printing that can be obtained by werbemittel or alike store or market point. In screen-printing, a design is separated into individual colors.

]]> By: Ali_niceone http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-102846 Ali_niceone Fri, 09 Dec 2011 18:09:00 +0000 http://talkingscience.org/blogs/?p=1696#comment-102846 Hello, I am here to share some awesome lines about Bohr's Model of Hydrogen. The simplest example of the Bohr Model is for the hydrogen atom (Z = 1) or for a hydrogen-like ion (Z > 1), in which a negatively-charged electron orbits a small positively-charged nucleus. Electromagnetic energy will be absorbed or emitted if an electron moves from one orbit to another. Only certain electron orbits are permitted. The radius of the possible orbits increases as n2, where n is the principal quantum number. The 3 → 2 transition produces the first line of the Balmer series. For hydrogen (Z = 1) this produces a photon having wavelength 656 nm (red light). But there are also some problems with the Bohr model -It violates the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit. -The Bohr Model provides an incorrect value for the ground state orbital angular momentum. -It makes poor predictions regarding the spectra of larger atoms. -It does not predict the relative intensities of spectral lines. -The Bohr Model does not explain fine structure and hyperfine structure in spectral lines. -It does not explain the Zeeman Effect. <a href="http://plastica.ch" rel="nofollow">Brustvergrösserung</a> Hello, I am here to share some awesome lines about Bohr's Model of Hydrogen.
The simplest example of the Bohr Model is for the hydrogen atom (Z = 1) or for a hydrogen-like ion (Z > 1), in which a negatively-charged electron orbits a small positively-charged nucleus. Electromagnetic energy will be absorbed or emitted if an electron moves from one orbit to another. Only certain electron orbits are permitted. The radius of the possible orbits increases as n2, where n is the principal quantum number. The 3 → 2 transition produces the first line of the Balmer series. For hydrogen (Z = 1) this produces a photon having wavelength 656 nm (red light).
But there are also some problems with the Bohr model
-It violates the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit.
-The Bohr Model provides an incorrect value for the ground state orbital angular momentum.
-It makes poor predictions regarding the spectra of larger atoms.
-It does not predict the relative intensities of spectral lines.
-The Bohr Model does not explain fine structure and hyperfine structure in spectral lines.
-It does not explain the Zeeman Effect. Brustvergrösserung

]]> By: Asif http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-102633 Asif Tue, 01 Nov 2011 13:20:00 +0000 http://talkingscience.org/blogs/?p=1696#comment-102633 And the mathematical steps are not supported by this page of blog so I did not posted them. And the mathematical steps are not supported by this page of blog so I did not posted them.

]]> By: Osam http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-102632 Osam Tue, 01 Nov 2011 13:18:00 +0000 http://talkingscience.org/blogs/?p=1696#comment-102632 Hi there, I am graduate and seeking admission for master's programme in Physics. So I want to share these lines also. these are informative lines. In the early 20th century, experiments by Ernest Rutherford established that atoms consisted of a diffuse cloud of negatively charged electrons surrounding a small, dense, positively charged nucleus. Given this experimental data, Rutherford naturally considered a planetary-model atom, the Rutherford model of 1911 – electrons orbiting a solar nucleus – however, said planetary-model atom has a technical difficulty. The laws of classical mechanics (i.e. the Larmor formula), predict that the electron will release electromagnetic radiation while orbiting a nucleus. Because the electron would lose energy, it would gradually spiral inwards, collapsing into the nucleus. This atom model is disastrous, because it predicts that all atoms are unstable. Also, as the electron spirals inward, the emission would gradually increase in frequency as the orbit got smaller and faster. This would produce a continuous smear, in frequency, of electromagnetic radiation. However, late 19th century experiments with electric discharges through various low-pressure gases in evacuated glass tubes had shown that atoms will only emit light (that is, electromagnetic radiation) at certain discrete frequencies. To overcome this difficulty, Niels Bohr proposed, in 1913, what is now called the Bohr model of the atom. He suggested that electrons could only have certain classical motions: The electrons can only travel in certain orbits: at a certain discrete set of distances from the nucleus with specific energies. The electrons of an atom revolve around the nucleus in orbits. These orbits are associated with definite energies and are also called energy shells or energy levels. Thus, the electrons do not continuously lose energy as they travel in a particular orbit. They can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency ν determined by the energy difference of the levels according to the Planck relation: where h is Planck's constant. The frequency of the radiation emitted at an orbit of period T is as it would be in classical mechanics; it is the reciprocal of the classical orbit period: The significance of the Bohr model is that the laws of classical mechanics apply to the motion of the electron about the nucleus only when restricted by a quantum rule. Although rule 3 is not completely well defined for small orbits, because the emission process involves two orbits with two different periods, Bohr could determine the energy spacing between levels using rule 3 and come to an exactly correct quantum rule: the angular momentum L is restricted to be an integer multiple of a fixed unit: where n = 1, 2, 3, ... is called the principal quantum number, and ħ = h/2π. The lowest value of n is 1; this gives a smallest possible orbital radius of 0.0529 nm known as the Bohr radius. Once an electron is in this lowest orbit, it can get no closer to the proton. Starting from the angular momentum quantum rule Bohr[2] was able to calculate the energies of the allowed orbits of the hydrogen atom and other hydrogen-like atoms and ions. Other points are: Like Einstein's theory of the Photoelectric effect, Bohr's formula assumes that during a quantum jump a discrete amount of energy is radiated. However, unlike Einstein, Bohr stuck to the classical Maxwell theory of the electromagnetic field. Quantization of the electromagnetic field was explained by the discreteness of the atomic energy levels; Bohr did not believe in the existence of photons. According to the Maxwell theory the frequency ν of classical radiation is equal to the rotation frequency νrot of the electron in its orbit, with harmonics at integer multiples of this frequency. This result is obtained from the Bohr model for jumps between energy levels En and En−k when k is much smaller than n. These jumps reproduce the frequency of the k-th harmonic of orbit n. For sufficiently large values of n (so-called Rydberg states), the two orbits involved in the emission process have nearly the same rotation frequency, so that the classical orbital frequency is not ambiguous. But for small n (or large k), the radiation frequency has no unambiguous classical interpretation. This marks the birth of the correspondence principle, requiring quantum theory to agree with the classical theory only in the limit of large quantum numbers. The Bohr-Kramers-Slater theory (BKS theory) is a failed attempt to extend the Bohr model which violates the conservation of energy and momentum in quantum jumps, with the conservation laws only holding on average. Bohr's condition, that the angular momentum is an integer multiple of ħ was later reinterpreted by de Broglie as a standing wave condition: the electron is described by a wave and a whole number of wavelengths must fit along the circumference of the electron's orbit: Substituting de Broglie's wavelength reproduces Bohr's rule. Bohr justified his rule by appealing to the correspondence principle, without providing a wave interpretation. In 1925 a new kind of mechanics was proposed, quantum mechanics in which Bohr's model of electrons traveling in quantized orbits was extended into a more accurate model of electron motion. The new theory was proposed by Werner Heisenberg. Another form of the same theory, modern quantum mechanics, was discovered by the Austrian physicist Erwin Schrödinger independently and by different reasoning. <a href="http://www.ychatter.com/AUS/flat_mate_finders.html" rel="nofollow">flat mate finders</a> Hi there, I am graduate and seeking admission for master's programme in Physics. So I want to share these lines also. these are informative lines. In the early 20th century, experiments by Ernest Rutherford established that atoms consisted of a diffuse cloud of negatively charged electrons surrounding a small, dense, positively charged nucleus. Given this experimental data, Rutherford naturally considered a planetary-model atom, the Rutherford model of 1911 – electrons orbiting a solar nucleus – however, said planetary-model atom has a technical difficulty. The laws of classical mechanics (i.e. the Larmor formula), predict that the electron will release electromagnetic radiation while orbiting a nucleus. Because the electron would lose energy, it would gradually spiral inwards, collapsing into the nucleus. This atom model is disastrous, because it predicts that all atoms are unstable.
Also, as the electron spirals inward, the emission would gradually increase in frequency as the orbit got smaller and faster. This would produce a continuous smear, in frequency, of electromagnetic radiation. However, late 19th century experiments with electric discharges through various low-pressure gases in evacuated glass tubes had shown that atoms will only emit light (that is, electromagnetic radiation) at certain discrete frequencies.
To overcome this difficulty, Niels Bohr proposed, in 1913, what is now called the Bohr model of the atom. He suggested that electrons could only have certain classical motions:
The electrons can only travel in certain orbits: at a certain discrete set of distances from the nucleus with specific energies.
The electrons of an atom revolve around the nucleus in orbits. These orbits are associated with definite energies and are also called energy shells or energy levels. Thus, the electrons do not continuously lose energy as they travel in a particular orbit. They can only gain and lose energy by jumping from one allowed orbit to another, absorbing or emitting electromagnetic radiation with a frequency ν determined by the energy difference of the levels according to the Planck relation:

where h is Planck's constant.
The frequency of the radiation emitted at an orbit of period T is as it would be in classical mechanics; it is the reciprocal of the classical orbit period:

The significance of the Bohr model is that the laws of classical mechanics apply to the motion of the electron about the nucleus only when restricted by a quantum rule. Although rule 3 is not completely well defined for small orbits, because the emission process involves two orbits with two different periods, Bohr could determine the energy spacing between levels using rule 3 and come to an exactly correct quantum rule: the angular momentum L is restricted to be an integer multiple of a fixed unit:

where n = 1, 2, 3, ... is called the principal quantum number, and ħ = h/2π. The lowest value of n is 1; this gives a smallest possible orbital radius of 0.0529 nm known as the Bohr radius. Once an electron is in this lowest orbit, it can get no closer to the proton. Starting from the angular momentum quantum rule Bohr[2] was able to calculate the energies of the allowed orbits of the hydrogen atom and other hydrogen-like atoms and ions.
Other points are:
Like Einstein's theory of the Photoelectric effect, Bohr's formula assumes that during a quantum jump a discrete amount of energy is radiated. However, unlike Einstein, Bohr stuck to the classical Maxwell theory of the electromagnetic field. Quantization of the electromagnetic field was explained by the discreteness of the atomic energy levels; Bohr did not believe in the existence of photons.
According to the Maxwell theory the frequency ν of classical radiation is equal to the rotation frequency νrot of the electron in its orbit, with harmonics at integer multiples of this frequency. This result is obtained from the Bohr model for jumps between energy levels En and En−k when k is much smaller than n. These jumps reproduce the frequency of the k-th harmonic of orbit n. For sufficiently large values of n (so-called Rydberg states), the two orbits involved in the emission process have nearly the same rotation frequency, so that the classical orbital frequency is not ambiguous. But for small n (or large k), the radiation frequency has no unambiguous classical interpretation. This marks the birth of the correspondence principle, requiring quantum theory to agree with the classical theory only in the limit of large quantum numbers.
The Bohr-Kramers-Slater theory (BKS theory) is a failed attempt to extend the Bohr model which violates the conservation of energy and momentum in quantum jumps, with the conservation laws only holding on average.
Bohr's condition, that the angular momentum is an integer multiple of ħ was later reinterpreted by de Broglie as a standing wave condition: the electron is described by a wave and a whole number of wavelengths must fit along the circumference of the electron's orbit:

Substituting de Broglie's wavelength reproduces Bohr's rule. Bohr justified his rule by appealing to the correspondence principle, without providing a wave interpretation.
In 1925 a new kind of mechanics was proposed, quantum mechanics in which Bohr's model of electrons traveling in quantized orbits was extended into a more accurate model of electron motion. The new theory was proposed by Werner Heisenberg. Another form of the same theory, modern quantum mechanics, was discovered by the Austrian physicist Erwin Schrödinger independently and by different reasoning. flat mate finders

]]> By: Salman http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-102631 Salman Tue, 01 Nov 2011 13:11:00 +0000 http://talkingscience.org/blogs/?p=1696#comment-102631 Hello, this is a wonderful and informative post about Boohr's atomic model. In atomic physics, the Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. This was an improvement on the earlier cubic model (1902), the plum-pudding model (1904), the Saturnian model (1904), and the Rutherford model (1911). Since the Bohr model is a quantum-physics–based modification of the Rutherford model, many sources combine the two, referring to the Rutherford–Bohr model. The model's key success lay in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen. While the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced. Not only did the Bohr model explain the reason for the structure of the Rydberg formula, it also provided a justification for its empirical results in terms of fundamental physical constants. The Bohr model is a primitive model of the hydrogen atom. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics, and thus may be considered to be an obsolete scientific theory. However, because of its simplicity, and its correct results for selected systems , the Bohr model is still commonly taught to introduce students to quantum mechanics, before moving on to the more accurate but more complex valence shell atom. A related model was originally proposed by Arthur Erich Haas in 1910, but was rejected. The quantum theory of the period between Planck's discovery of the quantum (1900) and the advent of a full-blown quantum mechanics (1925) is often referred to as the old quantum theory Hello, this is a wonderful and informative post about Boohr's atomic model. In atomic physics, the Bohr model, introduced by Niels Bohr in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. This was an improvement on the earlier cubic model (1902), the plum-pudding model (1904), the Saturnian model (1904), and the Rutherford model (1911). Since the Bohr model is a quantum-physics–based modification of the Rutherford model, many sources combine the two, referring to the Rutherford–Bohr model.
The model's key success lay in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen. While the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced. Not only did the Bohr model explain the reason for the structure of the Rydberg formula, it also provided a justification for its empirical results in terms of fundamental physical constants.
The Bohr model is a primitive model of the hydrogen atom. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader and much more accurate quantum mechanics, and thus may be considered to be an obsolete scientific theory. However, because of its simplicity, and its correct results for selected systems , the Bohr model is still commonly taught to introduce students to quantum mechanics, before moving on to the more accurate but more complex valence shell atom. A related model was originally proposed by Arthur Erich Haas in 1910, but was rejected. The quantum theory of the period between Planck's discovery of the quantum (1900) and the advent of a full-blown quantum mechanics (1925) is often referred to as the old quantum theory

]]> By: drv http://www.talkingscience.org/2009/04/the-bohr-atom/comment-page-1/#comment-35470 drv Mon, 10 May 2010 15:24:52 +0000 http://talkingscience.org/blogs/?p=1696#comment-35470 There are various flaws in the supposed model of the Bohr atom as it is pictured. There is only one electron and one proton in the hydrogen atom, whereas many are shown. In the Bohr model, the one electron rotates around the proton in a circular orbit. That leads to his derivation of the stable states. What is more important is that the radius of the Bohr atom is proportional to the square of the state number, while the energy level is simiarly inversely proportional to the state number. Therefore, the size of the Bohr atom is unlimited, which is a direct conflict to measurements. Bohr himself admitted that his model is "abstract". This problem led to the present Quantum Mechanics energy model of the atom in which the radius is undefined but limited to a range of values. This problem has recently been solved. See www.science-site.ScientificBreakthrough.htm . There are various flaws in the supposed model of the Bohr atom as it is pictured. There is only one electron and one proton in the hydrogen atom, whereas many are shown. In the Bohr model, the one electron rotates around the proton in a circular orbit. That leads to his derivation of the stable states.

What is more important is that the radius of the Bohr atom is proportional to the square of the state number, while the energy level is simiarly inversely proportional to the state number. Therefore, the size of the Bohr atom is unlimited, which is a direct conflict to measurements. Bohr himself admitted that his model is "abstract". This problem led to the present Quantum Mechanics energy model of the atom in which the radius is undefined but limited to a range of values.

This problem has recently been solved. See http://www.science-site.ScientificBreakthrough.htm .

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