Niels Bohr was born in Copenhagen on October 7, 1885. In 1911 did experimental work going on in the Cavendish Laboratory under J.J. Thomson's guidance and In 1912 he was at work in Rutherford’s laboratory in Manchester.[1]
Bohr's Experiment and Reasoning
In 1913 Bohr analysed the spectral lines of hydrogen. This meant that he observed the coloured lines (wavelengths given by a spectroscope). Since the lines were not continuous like rainbow, the electrons were not giving of energy continuously. Bohr concluded that the laws of basic physics did not abide to objects on an atomic scale. It was here when he proposed a new atomic model to explain the emission spectrum of hydrogen. [2]
Bohr agreed with Rutherford’s proposal that in the atom the electrons revolve around a central positively charged nucleus that is responsible for most of the weight of the atom. But from his special evidence, he concluded that electrons are found at only certain distances from the nucleus, and have particular values of energy. The further they are from the nucleus, the greater amount of energy they possess.[3] While in their orbit, electrons do not lose any energy. Bohr called the collection of electrons that orbits at any distance an electron shell. He found that the closer an electron is to the nucleus, the less energy it needs, but the farther away it is, the more energy it needs. The ground state of the atom was when the shells get closer and closer to one another, the further they are from the nucleus. He also found that the various energy levels can hold differing numbers of electrons: energy level 1 may hold up to 2 electrons, energy level 2 may hold up to 8 electrons, and so on.[4]
In 1913 Bohr analysed the spectral lines of hydrogen. This meant that he observed the coloured lines (wavelengths given by a spectroscope). Since the lines were not continuous like rainbow, the electrons were not giving of energy continuously. Bohr concluded that the laws of basic physics did not abide to objects on an atomic scale. It was here when he proposed a new atomic model to explain the emission spectrum of hydrogen. [2]
Bohr agreed with Rutherford’s proposal that in the atom the electrons revolve around a central positively charged nucleus that is responsible for most of the weight of the atom. But from his special evidence, he concluded that electrons are found at only certain distances from the nucleus, and have particular values of energy. The further they are from the nucleus, the greater amount of energy they possess.[3] While in their orbit, electrons do not lose any energy. Bohr called the collection of electrons that orbits at any distance an electron shell. He found that the closer an electron is to the nucleus, the less energy it needs, but the farther away it is, the more energy it needs. The ground state of the atom was when the shells get closer and closer to one another, the further they are from the nucleus. He also found that the various energy levels can hold differing numbers of electrons: energy level 1 may hold up to 2 electrons, energy level 2 may hold up to 8 electrons, and so on.[4]
Explaining the Spectra
Bohr’s atomic theory also helped to explain the spectra. He explained the discrete lines on the hydrogen spectra by proposing if a hydrogen atom was given energy, an electron can jump to a higher shell, away from the nucleus. However they will always return back to their ground state as the atom will be unstable.[5]
Bohr’s atomic theory also helped to explain the spectra. He explained the discrete lines on the hydrogen spectra by proposing if a hydrogen atom was given energy, an electron can jump to a higher shell, away from the nucleus. However they will always return back to their ground state as the atom will be unstable.[5]
Other Discoveries
Bohr's theoretical work contributed significantly to scientists' understanding of nuclear fission. This is when an atom contains protons and neutrons in its central nucleus. In fission, the nucleus splits, because it has been bombarded by other subatomic particles known as neutrinos. The resulting pieces have less combined mass which is converted into nuclear energy. According to his liquid droplet theory, a liquid drop provides an accurate representation of an atom's nucleus. This theory was instrumental in the first attempts to split uranium atoms in the 1930s, an important step in the development of the atomic bomb.[6]
Bohr's theoretical work contributed significantly to scientists' understanding of nuclear fission. This is when an atom contains protons and neutrons in its central nucleus. In fission, the nucleus splits, because it has been bombarded by other subatomic particles known as neutrinos. The resulting pieces have less combined mass which is converted into nuclear energy. According to his liquid droplet theory, a liquid drop provides an accurate representation of an atom's nucleus. This theory was instrumental in the first attempts to split uranium atoms in the 1930s, an important step in the development of the atomic bomb.[6]
[1] Palermo, E. 2014. Niels Bohr: Biography & Atomic Theory. [online] Available at: http://www.livescience.com/32016-niels-bohr-atomic-theory.html [Accessed: 10 Mar 2014].
[2] Sharwood, J. and Corrigan, D. 2007. Nelson chemistry. South Melbourne: Thomson Learning.
[3] Siegfried, T. 2013. When the atom went quantum: Bohr's revolutionary atomic theory turns 100. Science News, 184 (1), pp. 20--24.
[4] Sharwood, J. and Corrigan, D. 2007. Nelson chemistry. South Melbourne: Thomson Learning.
[5] [ article]
Article title: Resisting the Bohr Atom: The Early British Opposition
Author: Kragh, Helge. Published in: PHYS PERSPECT, v. 13 no. 1, pp. 4-35 Date: 2011
ISSN: 1422-6944
[6] Faye, J. 1991. Niels Bohr: His heritage and legacy.
[2] Sharwood, J. and Corrigan, D. 2007. Nelson chemistry. South Melbourne: Thomson Learning.
[3] Siegfried, T. 2013. When the atom went quantum: Bohr's revolutionary atomic theory turns 100. Science News, 184 (1), pp. 20--24.
[4] Sharwood, J. and Corrigan, D. 2007. Nelson chemistry. South Melbourne: Thomson Learning.
[5] [ article]
Article title: Resisting the Bohr Atom: The Early British Opposition
Author: Kragh, Helge. Published in: PHYS PERSPECT, v. 13 no. 1, pp. 4-35 Date: 2011
ISSN: 1422-6944
[6] Faye, J. 1991. Niels Bohr: His heritage and legacy.