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Scientists and Theories of Atomic Structure

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Maryam Khan Scientists and atomic structure The structure of an atom has taken many years to develop as what we now know it to be. It consists of the hard work of many scientists, their developments and theories. Since 400BC from when the atom model was just a ball to 1913 when it became the bohr model and the atom which we now know it to be. The first of many people who played a role in this vital development of the atomic structure is the Greek philosopher Democritus with his theory of the ?atomos? meaning ?not to be cut?. Democritus was quite ahead of his time with this study and discovery. He began his research for a description of matter - Could it divided forever or is there a limit to how many times it can be divided. He later concluded that the atom was like a billiard ball that couldn?t be split any further and this is what you would end up with if you divided a sample of matter so many times and therefore was ?indivisible?. His theory stated that atoms were small, hard particles all made up of the same material however they were different shapes and sizes. He also said that these indivisible pieces (atoms) were infinite ? always moving and capable of moving together. ...read more.


Around the same time of Thomson, a lady called Marie Curie also came to the same conclusion that some atoms (at least the one she was studying) are divisible. Her contribution to the development of the atomic structure was not direct but still mattered because it was a revolutionary discovery disproving those that came before her. She discovered and isolated radium, a new element which spontaneously disintegrated into other elements- She called this process ?radioactivity?. Through continued systematic studies of the different chemical compounds gave the surprising result that the strength of the radiation didn?t depend on the compound that was being studied. Marie came to the conclusion that the ability to radiate must be linked to the interior of the atom itself as oppose to the arrangement of the atoms in a molecule. This proved that the atoms of one element at least were not indivisible and therefore disproving Dalton?s theory. However Thomson had already discovered sub-atomic particles so in all fairness Marie Curie didn?t really change anything ? she just added to this idea of atoms being divisible. Nevertheless the ?plum pudding model? was later disproved by Ernest Rutherford who is known as the ?father of nuclear physics? due to pioneering of the orbital theory of the atom with his famous much anticipated gold foil experiment. ...read more.


The negatively charged electron and the overall neutral charge of an element would mean that something balanced out the charges so there must be a positive charge within the atom. In 1918 Rutherford discovered the ?proton? whilst performing his various experiments in the field of radioactivity, bombarding nitrogen gas with alpha particles - he noticed that one of the experimental results was a flow of hydrogen. Him and others carried out a number of experiments, transmuting one atom into another by striking it with high energy ? particles and each time hydrogen nuclei were emitted. He correctly deduced that the hydrogen atoms must have come from within the nitrogen atoms themselves, which would mean that there was something within all of these atoms which was divisible, the amount of which would determine the charge of the nucleus in the atom. This integer was the number of hydrogen nuclei or ?protons? so therefore the particle Rutherford isolated was the proton. Finally, in 1932 an English physicist named James Chadwick bombarded light elements with high energy alpha particles. He found that a new type of radiation was emitted much more penetrating than any that had been detected before. He showed that this new type of radiation was made up of uncharged particles with approximately the same mass as a proton, known as neutrons. This discovery took place roughly after 20 years http://chemistry.about.com/od/historyofchemistry/p/rutherford.htm http://www.ucc.ie/academic/chem/dolchem/html/dict/atom.html http://atomictimeline.net/index.php http://www.nobelprize.org/nobel_prizes/physics/articles/curie/ http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm http://www.physlink.com/education/askexperts/ae46.cfm ...read more.

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The candidates introduction is fairly good but could still be improved, they have used background information to try and engage the reader which is a good thing as this makes it more likely that they will read all of your ...

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Response to the question

The candidates introduction is fairly good but could still be improved, they have used background information to try and engage the reader which is a good thing as this makes it more likely that they will read all of your essay rather than simply skim through it. However an introduction should also include a few sentences that introduce your topic, in this case you should say what the atom is. Finally you should state exactly what you plan to discuss so that the purpose of your essay is clear. Overall the candidates response is good and they have demonstrated a clear understanding of this topic.

Level of analysis

It is evident that the candidate has taken the time to research the history of the atom, it is important to research scientific topics as this helps to make sure that you get your facts correct. Furthermore it demonstrates an ability to work independently and it shows enthusiasm for your subject, which is always a good thing. To add to this, the candidate has sensibly included links to the online resources they have used, this is important as it shows the steps you have taken to prepare for your essay and can show that your work is not plagiarised. Unfortunately, the candidate has not concluded this essay, you should always write a conclusion, this is your opportunity to leave the reader with a good impression of your work. A good conclusion summarises key points form within you essay and states why these are important, this helps you tie together any loose ends and bring your essay to a close. You should also write a personal response, for a science based essay you could state what you have learnt from researching your topic.

Quality of writing

In general the layout of this essay is fine but I don’t recommend using bullet points, it is far better to write information in continual prose. That said, this essay is well written, the candidate links their points together nicely and there are no grammatical or spelling errors.

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