environmental sciences

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A Look At Niels Bohrs Atomic Structure Environmental Sciences Essay

Niels Bohr was born in 1885 in Copenhagen, to a family who valued education and science above all else. His father, Christian Bohr, was a professor of psychology at the University of Copenhagen. His grandfather was a director of a school in Bornholm. His aunt, Hannah Adler, was a teacher, and later in life founded her own school. She became one of the first two Danish women doctorates in physics. In fact, education was one of the reasons why Niels’ parents have met – his mother, Ellen Adler, wanted to become Christian’s student, but instead became his wife. They married outside of church

He was second of three children. While little is known about his elder sister (some writers don’t even mention her existence), Borh was particularly close to his younger brother, Harald. They were practically inseparable since childhood. In fact, the two year difference between them was particularly vexing for them when Niels started his schooling – he couldn’t bear the thought of not being educated together. Harald, though, followed his beloved brother faithfully, always so eager to catch up. Therefore, despite considering Niels to be a more brilliant scientist than he was, and despite the fact that he was very talented in many areas (he even made it to the Danish Olympic football team in 1908), eventually he became a renowned mathematician.

From the young years Niels Bohr was somewhat of a dreamer, very much involved in his own thoughts. He was not very witty when it came to common things, but anything concerning science came to him with a relative ease. His university classmates said that he almost had an inexplicably different manner of thinking that they did. In fact, he often criticized the errors in his physics textbook that his professor would miss. He would not consider stating something that he knew to be false.

Through his early university years he was also very much concerned about philosophy, and such things like a freedom of choice. He and his friends have spent a long time trying to describe it from the mathematical point of view. During his second year he even considered writing a paper on philosophy. This was not to be, though, because his physics professor has assigned him to write a report about radioactive transformations. Upon the success of this report his advisor suggested him to work on examining the properties of surface tensions – a work which earned him a gold medal from the Royal Danish Academy of Sciences and Letters. From there he continued his work in physics in electrical theory and in just a couple of years, in 1911, he received his doctorate.

Later that year he moved to Cambridge, where he first met Thomson who kept avoiding reading his paper, and then Rutherford, who was very frustrated at the time at the lack of interest in his work. The latter meeting gave birth do a deep friendship. Therefore just half a year after arriving he left Cambridge and followed Rutherford to Manchester. There he started working with the planetary model of an atom.

Part 2

It was in Manchester, in 1912, when Bohr started working on it. His colleague, Hevesy, was experiencing great troubles separating a quantity of lead from radium-d. While their atomic mass was clearly different, their properties were identical. Rutherford did not have an answer to this problem with his model – in fact, he considered there be too few experimental data in order to have any sort of explanation. But one night Hevesy decided to confide in Bohr, who didn’t know any better and found a solution. It became immediately clear to him that the order in Periodic Table should be governed not by mass of the core of the atom, as was thought previously, but by its charge. And so, as radium undergoes a radioactive decay, it must lose an alpha particle that has a charge +2, making the properties of the remaining material indistinguishable from lead.

One problem with the planetary model was, though, is the stable size of an atom. All the theories have predicted that electrons would just collapse into the nucleus. So Bohr theorized that, perhaps, may be electrons form a ring around the core, repulsing each other and preventing the collapse. He calculated that there should not be too many electrons in a ring – no more than 7, otherwise they would start forming a second ring. Although, while those rings would have been indeed stable, it did not guarantee the stability of size. So Bohr declared that there should only oscillate with a set frequency, thus, be unable to leave their orbits, thus abandoning hope for a classical mechanical explanation.

Once Rutherford has learned of this theory, he wanted him to simplify the matter by following only on the atomic hydrogen. He also told him no to hurry too much. In part, because he himself was not ready for it. In part, because he thought that no one else was working on the explanation. He couldn’t have been more wrong, though.

A British physicist, Nicholson tried to explain structure of atoms within stars and nebulae. He had similar thoughts on the matter. He also put electrons in rings around the nucleus. And he also was forced to limit the acceptable frequencies of oscillation. But their conclusions were too different. Nicholson did not try to achieve permanent stability; he just wanted to have temporary ever so changing constructions. Using this model he tried to explain the spectral lines.

At first, Bohr was puzzled by the resulting model, but he reconciled it with himself that he and Nicholson tried to describe an atom in a different states. He, who at that time didn’t even bother to look at the spectral lines, considered that the stability and radiation of the atom to be completely different problems. Besides, he did not find Nicholson’s explanation attacking the core of the question – why those lines were there.

But then, in early February of 1913, Bohr was explaining his theory to one of his college classmates. And he was asked a question – how did his theory explain spectral formulas. In the past, though, he had never even heard about any sort of spectral formulas. But once he looked at them he could help but hurry – he was afraid that something so obvious would be immediately noticed by someone else. He realized that those formulas referred to two energy levels – energy before the emission and after. The first one was variable, but could have only set values. The second one was constant for all, the “bottom”, the lowest energy that it would be possible to have. And the difference between them is the energy emitted.

He saw a ladder out of those formulas. The only thing that can emit that energy would be electrons, and they would emit it only in transition from one orbit to another. While they are on orbits they would not radiate.

Part 3

What results came from this model… First, it cannot be helped but to note that his model was wrong. Or, to be precise, not entirely correct. At that early age, though, just couple of years after physicists started to try to challenge classical models, at about the same time with Einstein’s postulate of general relativity, and a decade away from formulation of quantum physics… One cannot help but appreciate what kind of potential for development it has brought.

Even now, many people without formal physical education, though they would probably know that there exists somewhere such a weird thing called quantum physics, but they don’t really know what it is. They are told that everything is made out of protons, with electrons zipping around them, and the planetary model just naturally comes to mind. Even some of the physicists, who accept quantum physics for what it is and know the principles behind it, cannot completely imagine objects whose position is given by a set of probabilities. And here again, Bohr’s model is visually somewhat close enough to be comparable to the truth.

The reason for it is quite simple. Bohr saw his atom in a manner similar to that of a half-blind person without glasses. He knew that it was still blurry, but compared to what other people saw it has showed an incredible clarity. He made a lens for other people to use, then, still very rough, that allowed everyone else to see what he saw. Those who came after him refined this lens to the point of the model that we know and understand today, even though lens-maker’s knowledge is required to appreciate all its beauty. For everyone else, though, Bohr’s glasses are still available on the market, with a side note that they allow the smallest amount of precision.

At that time especially, planetary model was an incredible breakthrough. It added new depth to physics – quantum jumps – to already familiar quantized matter and quantized energy. Some people thought him to be mad. Some openly laughed at him. Some questioned the very basic premise of it. But there were those as well who saw it for all the potential that it truly had.

He was the most classical out of the all modern physicists. Thus, he was able to create his model only as far as his classical roots allowed him to go. And while as he grew to understand everything that his model made now possible, he managed to reconcile the break from the classics through both correspondence and complementarity principle. But it was up to his students, particularly Heisenberg, to shape the rest.


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