Rutherford could imagine the basic structure of atoms through interactions between matter. However, it has been the interaction between light and matter that has given more clues to understanding the atom. Several of these tracks are known for some time, but nevertheless, results were scattered to the discovery of the match as it was not known.
emission and absorption spectra
spectroscopy is a technique that is beginning to develop in the eighteenth century. White light is composed of different colors. When together they perceive that white appearance. Spectroscopy light breaks in each of its component colors, shows spectrum. This technique was used to identify different elements in gases by emission and absorption spectra.
For an emission spectrum is subjected to high temperature gas to emit light. In an absorption spectrum, a beam of white light passes through a container of cold gas. In both cases, the final light (issued or has passed through the gas) passes through a prism and breaks into colors. In the case of the broadcast spectrum are broken so only narrow lines of a single color. In the absorption spectrum, the spectrum is almost complete, showing all colors, except for a darker lines, which correspond to the same wavelength as those seen in the emission of the same element.
The decomposition of the spectrum of each gas is unique, so it is possible to identify elements. J. von Fraunhofer (1787-1826) recorded the spectrum of sunlight, instead of a gas. He noted how there were lines darker than others. That is, take an absorption spectrum, with the "gas" to analyze the sun itself later, Gustav Kirchoff (1824-1887) showed that some of these dark lines coincide with lines sodium and other elements, showing that the Sun is composed of atoms identical to those on Earth.
Undoubtedly, these emission and absorption spectra were revealing interesting aspects of the internal structure of atoms. However, the knowledge available at that time was not sufficient to establish a clear and consistent.
Balmer lines
The scientists focused on the emission and absorption lines of hydrogen, being the simplest. Johann J. Balmer (1825-1898), Swiss mathematician, succeeded in establishing a relationship mathematical reproduced the observed light frequencies, f . The interesting thing was that the relationship used integers, n i n f :
(where R is the Rydberg constant , R = -1 3.2867e15 s)
Despite not understanding what it really meant this formula Balmer able to describe the visible lines of hydrogen, as n f = 2, which is called the Series Balmer, and predict the existence of other series, that was later confirmed: for n f = 1 (Lyman series lines, ultraviolet) n f = 3 (number of patches, infrared lines) and n f = 4 (Brackett series in the infrared)
Quantum mechanics
Rutherford's atom was assumed that the electrons spinning away from around the atomic nucleus, as if it were a solar system. This model provided the atoms continuously emit radiation, according to Maxwell's electromagnetism, losing energy and spiraling to its disintegration. The model was a good step, and defining the structure of atoms, consistent with particle bombardment experiments, but it was not right, nor loomed no hint anywhere that would derive the Balmer formula.
1900 is a major discovery: the quantum of radiation. A black body is defined as one capable of absorbing all the incident radiation, without showing anything. On the other hand, any body, to be at a given temperature emits radiation, and in particular to a black body this issue depended only on its temperature, and not its form or type of material. The radiation emitted by the black body brought from head to scientists of the time, because they were not able to explain.
Max Planck (1858-1947) found a mathematical relationship explaining the issue, but she needed at that time an extraordinary hypothesis: a spectrum of electromagnetic radiation as the black-body energy is not distributed equally, but at each frequency corresponds to a fixed amount (a As ) proportional to its frequency, and therefore the total energy for a given frequency is a multiple of the minimum energy. A frequency f, has an associated energy hf (where h is Planck's constant, h = 6.62e-34 J • s). A light source that emits only at that frequency, total energy issue is an integer multiple of hf, an energy issue 1 • hf, or 2 • hf, or 5 • hf, etc, but never delivered 0.5 • hf1, or 2.45 • hf1.
The Bohr hydrogen atom
Planck showed that energy was quantized electromagnetic waves were multiples of a minimum energy, one quantum. On the other hand, the emission and absorption spectra could be described by a formula using whole numbers. It was the Danish physicist Niels Bohr (1885-1932) who took these seemingly unrelated data to make his model of atom.
Bohr agreed with Rutherford that the electrons should rotate around the nucleus, but certain conditions had to exist to prevent its destruction. The Rutherford atom, there were no restrictions, any orbit was possible. Bohr's hypothesis was that could only exist certain orbits, those such that its angular momentum be a multiple of Planck's constant . Ie the distance from the nucleus to which an electron can orbit is quantized with a minimum value . He added as a postulate that the electrons in these orbits do not emit radiation.
With this model of the atom, electrons that change must win or lose orbital energy with a very specific, dependent on the initial orbit and the final orbit. In developing these ideas, Bohr came to the Balmer formula. The Bohr atom describes the electrons in the hydrogen atom around a single integer n , which indicates the orbit it occupies. The meaning of the Balmer formula is that a transition from an initial level i n , until a final level n f absorbs radiation when an electron goes into a higher orbit (n greater than n f i ) or emits radiation if the final orbit is below the initial (N f i less than n )
The frequency (or energy) of this radiation has to be the exact to be absorbed. If it is higher or lower will not be. Similarly, the energy emitted is always the same. The set of electromagnetic waves that could emit or absorb a discrete set, as had been observed in spectra from the eighteenth century.
The Bohr atom was based on classical physics , considering the electrons as particles orbiting around a nucleus, and I applied the first concepts of quantum physics. And introduced the concept of quantum number, n number that identifies the orbit in which the electron is. The model explains perfectly the hydrogen atom, ie an atom with one electron. But it was not accurate for most electron atoms. This requires introducing more quantum numbers, describing other characteristics of the orbits that Bohr did not contemplate. Annexes
For the (relative) simplicity of the theoretical calculations, add in separate entries for whom it may concern:
- Calculating radius of Bohr orbits
- Deduction Balmer's formula from the Bohr atom
emission and absorption spectra
spectroscopy is a technique that is beginning to develop in the eighteenth century. White light is composed of different colors. When together they perceive that white appearance. Spectroscopy light breaks in each of its component colors, shows spectrum. This technique was used to identify different elements in gases by emission and absorption spectra.
For an emission spectrum is subjected to high temperature gas to emit light. In an absorption spectrum, a beam of white light passes through a container of cold gas. In both cases, the final light (issued or has passed through the gas) passes through a prism and breaks into colors. In the case of the broadcast spectrum are broken so only narrow lines of a single color. In the absorption spectrum, the spectrum is almost complete, showing all colors, except for a darker lines, which correspond to the same wavelength as those seen in the emission of the same element.
The decomposition of the spectrum of each gas is unique, so it is possible to identify elements. J. von Fraunhofer (1787-1826) recorded the spectrum of sunlight, instead of a gas. He noted how there were lines darker than others. That is, take an absorption spectrum, with the "gas" to analyze the sun itself later, Gustav Kirchoff (1824-1887) showed that some of these dark lines coincide with lines sodium and other elements, showing that the Sun is composed of atoms identical to those on Earth.
Undoubtedly, these emission and absorption spectra were revealing interesting aspects of the internal structure of atoms. However, the knowledge available at that time was not sufficient to establish a clear and consistent.
Balmer lines
The scientists focused on the emission and absorption lines of hydrogen, being the simplest. Johann J. Balmer (1825-1898), Swiss mathematician, succeeded in establishing a relationship mathematical reproduced the observed light frequencies, f . The interesting thing was that the relationship used integers, n i n f :
(where R is the Rydberg constant , R = -1 3.2867e15 s)
Despite not understanding what it really meant this formula Balmer able to describe the visible lines of hydrogen, as n f = 2, which is called the Series Balmer, and predict the existence of other series, that was later confirmed: for n f = 1 (Lyman series lines, ultraviolet) n f = 3 (number of patches, infrared lines) and n f = 4 (Brackett series in the infrared)
Quantum mechanics
Rutherford's atom was assumed that the electrons spinning away from around the atomic nucleus, as if it were a solar system. This model provided the atoms continuously emit radiation, according to Maxwell's electromagnetism, losing energy and spiraling to its disintegration. The model was a good step, and defining the structure of atoms, consistent with particle bombardment experiments, but it was not right, nor loomed no hint anywhere that would derive the Balmer formula.
1900 is a major discovery: the quantum of radiation. A black body is defined as one capable of absorbing all the incident radiation, without showing anything. On the other hand, any body, to be at a given temperature emits radiation, and in particular to a black body this issue depended only on its temperature, and not its form or type of material. The radiation emitted by the black body brought from head to scientists of the time, because they were not able to explain.
Max Planck (1858-1947) found a mathematical relationship explaining the issue, but she needed at that time an extraordinary hypothesis: a spectrum of electromagnetic radiation as the black-body energy is not distributed equally, but at each frequency corresponds to a fixed amount (a As ) proportional to its frequency, and therefore the total energy for a given frequency is a multiple of the minimum energy. A frequency f, has an associated energy hf (where h is Planck's constant, h = 6.62e-34 J • s). A light source that emits only at that frequency, total energy issue is an integer multiple of hf, an energy issue 1 • hf, or 2 • hf, or 5 • hf, etc, but never delivered 0.5 • hf1, or 2.45 • hf1.
The Bohr hydrogen atom
Planck showed that energy was quantized electromagnetic waves were multiples of a minimum energy, one quantum. On the other hand, the emission and absorption spectra could be described by a formula using whole numbers. It was the Danish physicist Niels Bohr (1885-1932) who took these seemingly unrelated data to make his model of atom.
Bohr agreed with Rutherford that the electrons should rotate around the nucleus, but certain conditions had to exist to prevent its destruction. The Rutherford atom, there were no restrictions, any orbit was possible. Bohr's hypothesis was that could only exist certain orbits, those such that its angular momentum be a multiple of Planck's constant . Ie the distance from the nucleus to which an electron can orbit is quantized with a minimum value . He added as a postulate that the electrons in these orbits do not emit radiation.
With this model of the atom, electrons that change must win or lose orbital energy with a very specific, dependent on the initial orbit and the final orbit. In developing these ideas, Bohr came to the Balmer formula. The Bohr atom describes the electrons in the hydrogen atom around a single integer n , which indicates the orbit it occupies. The meaning of the Balmer formula is that a transition from an initial level i n , until a final level n f absorbs radiation when an electron goes into a higher orbit (n greater than n f i ) or emits radiation if the final orbit is below the initial (N f i less than n )
The frequency (or energy) of this radiation has to be the exact to be absorbed. If it is higher or lower will not be. Similarly, the energy emitted is always the same. The set of electromagnetic waves that could emit or absorb a discrete set, as had been observed in spectra from the eighteenth century.
The Bohr atom was based on classical physics , considering the electrons as particles orbiting around a nucleus, and I applied the first concepts of quantum physics. And introduced the concept of quantum number, n number that identifies the orbit in which the electron is. The model explains perfectly the hydrogen atom, ie an atom with one electron. But it was not accurate for most electron atoms. This requires introducing more quantum numbers, describing other characteristics of the orbits that Bohr did not contemplate. Annexes
For the (relative) simplicity of the theoretical calculations, add in separate entries for whom it may concern:
- Calculating radius of Bohr orbits
- Deduction Balmer's formula from the Bohr atom
