Atomic Theory - Essay

Topics: Atom, Chemical element, Electron Pages: 5 (1540 words) Published: October 25, 2011
Atomic theory is the idea that matter is made up of small particles made of atoms. The atomic theory first had 5 points which were stated by John Dalton who came up with it. The first one was that all elements were made up of small units called atoms. The second one was that all atoms of a given element are identical to each other. Third, all the atoms were different from all the other atoms. Fourth, atoms of different elements combined together in equal numbers to form compounds. Fifth and final, atoms cannot be broken down, created or divided.

John Dalton was a chemist in the early 19th century and his work was focused on the behavior and properties of gases. He used his work on gases to come up with his law of proportions which was true to the smallest particle or atom. He then found out that he could use that to find the atomic weight of each element. When John Dalton created his atomic theory, it was based on simple deductive reasoning and was later; testing by his successors proved that the majority of his theory was correct. From the atomic theory created by John Dalton, Neil Bohr a physicist was able to create his own theory, the Bohr Atomic theory that was about an atoms structure and more on its atomic weight.

John Dalton’s atomic theory was not perfect, it had its flaws, but it went above and beyond during its time. Some of the problems with Dalton’s theory are that his second law that all atoms of the same element are the same is false because today we have found that there are other kinds of atoms called isotopes. An isotope is an atom that has the same amount of electrons and protons, but it has more neutrons that increase its atomic mass. Some examples of isotopes are Carbon 12, carbon 13, carbon 14, Uranium (234, 235, and 238) and lithium (6, 7). Carbon 14 is especially useful because we know its rate of decay and can use to find how old an object is due to the fact that everything absorbs carbon 14 until they die and then they start to decay. Using carbon 14, you find how old something is.

Another problem with Dalton’s theory was discovered in rule 4, but in the second part that states that all atoms join together in equal numbers. This is obviously contradicted because we have a compound such as H2O which is not in equal numbers. If his rule was completely true, it would have to be HO which is a hydrogen ion.

The last part of his theory, rule number 5 which talks about that atoms cannot be created, destroyed, or divided is partly false because of nuclear fission, we know that it is possible to split and atom and as a result, you release a lot of energy. Nuclear fission is the process of shooting a neutral particle at an unstable atom like uranium and having it break apart sending more particles to other atoms of uranium exponentially increasing in power.

Even thought Dalton’s theory had its problems, his ideas where made from basic reasoning and since it was discovered in the 1800’s, this discovered was ahead of its time. With the development of the microscope and future experiments made, we soon learned that atoms are made of 3 sub-particles called electrons, protons, and neutrons. We then went on to scientifically create a field around the atom where we can predict the path of electrons and how they can interact with other atoms to form certain bonds; bonds such as ionic bonds and covalent bonds which create most of the compounds that we interact with in our daily life.

Year Scientist(s) Discovery

eraDemocritus"by convention bitter, by convention sweet, but in reality atoms and void" 1704Isaac NewtonProposed a mechanical universe with small solid masses in motion. 1803John DaltonProposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. 1832Michael Faraday

Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of...
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