John Daltons Atomic Theory - Essay Example

Democritus had first suggested that the atom existed, but no conclusive studies had been carried out to prove its existence (Vasilescu & Adrian-Scotto, 2010). There was also no way of explaining why different compounds reacted or combined in different proportions with various gases. Joseph Proust analyzed oxides of tin and realized that the masses of tin dioxide and tin (II) oxide were made up of either 78.7% Sn and 21.3 O, and 88.1% Sn and 11.9% O respectively. This motivated John Dalton to study what makes different reactions unique.

Development of the Atomic Theory

Dalton formulated the theory after carrying out experiments on the behavior of various gases. These experiments were based on 2 laws. The first was the law of conservation of mass (by Antoine Lavoisier) which posits that the overall mass in a chemical process does not change (Dial, et al., 2009). The next law was the law of definite proportions (by Joseph Proust) which posits that when a compound is stripped into its basic elements the masses of the basic elements will have similar quantities, irrespective of the amount of the original material. As a follow-up to the experiment conducted by Proust on oxides of tin, John Dalton conducted the same experiment on the oxides of tin. He also experimented with water and how it absorbed carbon dioxide and nitrogen. Dalton also started the study of various atomic weights depending on the combinations of the mass proportions, while taking the hydrogen atom as the base standard. 

From the laws, Dalton established the law of multiple proportions that posits that when 2 chemical elements combine to produce more than one likely compound then the proportion of the second element’s mass that joined with a specific mass of the first element will be represented as proportions of whole numbers (Niaz, 2001). The results of this laid the foundation for Dalton’s Atomic Laws. These are made up of five theorems. The first theorem posits that an element, in its unmixed state, is made up of particles referred to as atoms. The second posits that all the atoms in a particular element are similar. The third posits that distinguishing atoms belonging to different elements can be done by using their different atomic weights. Fourth, compounds are made when atoms are combined. And lastly, it is not possible to either create or destroy atoms in a chemical reaction, the only thing that changes is the grouping. Previous chemists were not able to make the breakthroughs that Dalton made because in the times before him, the laboratory instruments that existed were very crude and could not make small, precise measurements.

Dalton’s development of the atomic model made it possible for more researchers and scholars to study the atom in greater detail. In 1897, J.J. Thomson discovered the electron, and his discovery opened people’s eyes to the fact that atoms were made up of tinier particles. By this time, however, the discovery of the atomic nucleus was still years away, and therefore the plum pudding model was proposed in 1904. The model states that the atom is composed of electrons that drift freely in a soup made of positive charges. The model did not explain how the electrons were organized inside the atom (Hon & Goldstein, 2013). In 1911 Ernest Rutherford established the planetary model of the atom that stated that the protons were found in the nucleus of the atom and then put the electrons in orbiting paths around the nucleus (Nagendrappa, 2011). Niels Bohr further developed Rutherford’s model by putting forward the idea that the orbiting electrons could only move around the nucleus in definite orbits at distinct energy levels around the atom nucleus (Prasad, 2013).

Conclusion

John Dalton played a crucial role in setting the ball in motion regarding studies about the nature of the atom, and how the atoms in an element came together in various proportions to form compounds. He pioneered the way for the likes of J.J. Thomson, Ernest Rutherford, and Niels Bohr to carry out further studies on the structure of the atom. As he had better laboratory instruments with which to carry out scientific experiments than those possessed by his predecessors, the scientists that came after him used advanced methods and apparatus to make the discoveries that added to what John Dalton had started.

The models used currently do not rely on John Dalton’s Atomic Theory. Numerous changes that occurred in the fields of quantum chemistry, relativity, and uncertainty in the 1920s obligated chemists to review the currently-held ideas regarding atoms and their structures. They reduced their reliance on physical models (that for instance described an electron as a small particle, possessing an electrical charge and moving in a specific path at a specific speed and part of the atom) and placed more emphasis on mathematical models. They searched for mathematical equations that, when answered, would give the precise solutions for the mass, spin, speed, and charge, as well as numerous other characteristics of the electron (Ghosh, et al., 2013).