Over the past 200 years, scientists have come up with many different models of the structure of an atom. Although atoms are too small to look at clearly, scientist such as Lord Ernest Rutherford were able to perform a number of experiments which helped them to understand their properties. Lord Ernest Rutherford Lord Ernest Rutherford, born in 1871, was a New Zealander chemist and physicist who was the first person to split an atom (Biography, 2019). When he finished school, Rutherford won a scholarship to study in England at Cambridge University, later becoming a professor at McGill University in Montreal. Rutherford is most well-known for his Gold Foil experiment, in which he made discoveries that led him to his conclusions about his Atomic Model. He also discovered that uranium would give off different kinds of rays, something that is now known as radioactive material (Lafferty, 1992).
Through his experiments, he found that atoms could be changed and broken down into smaller parts and that atoms had a dense nucleus as their centre surround by empty space. He also made the discovery of how to induce the nuclear reaction of a stable element, artificially. Rutherford received many honour for his work, including the 1908 Nobel Prize for Chemistry, as well as numerous fellowship and honorary degrees from several organisations. His various achievements and discoveries over his life led to Rutherford being dubbed the ‘Father of the Nuclear Age’. Earlier models of the atom There were multiple models of the atom that had been developed before Rutherford, that he managed to disprove. Democritus, who lived around 450 BC, was the first to suggest that everything was made up of small, indivisible, solid particles. He believed that if something was to be continually broken in half, it would reach a stage where it could be broken down no further. This idea was not widely accepted, as people preferred to believe the ideas that had already been suggested (Abcte, 2019). John Dalton’s model was similar to Democritus’, suggesting that all matter was made up of very small particles called atoms.
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The ideas of the nucleus and electrons were not yet known; however, his theories were still widely accepted as were considered to be explaining the Law of the Conservation of Mass, as well as other observations previously made, including definite and multiple proportions. John Joseph Thomson determined that atoms were made up of smaller particles, negative electrons as well as material which was positively charged. Thomson’s model is known as the Plum Pudding model, as he believed that electrons were distributed like plums throughout the positively charged material, which could be depicted as the cake (Silvester, 2015). Rutherford’s model Also known as the planetary model, or nuclear atom, the atomic model that Rutherford proposed showed a nucleus of a positive charge as a core, a tiny dense centre, where most of the atom’s mass is found. This was surrounded by electrons of a negative charge circling the nucleus from a decent distance away, similar to planets orbiting the sun (Encyclopaedia Britannica, 2019). Rutherford was the first to show that atoms had a nucleus, but it wasn’t until 1932, that James Chadwick suggested the nucleus contained neutrons (Cox and Parsonage, 1993).
To draw his conclusions, Rutherford performed his famous Gold Foil Experiment. Based on Marie Curie’s discovery, he knew that a radioactive substance’s radiation would make a mark on photographic paper. When he placed a piece of gold in the way of the radiation beam, he discovered that the marks remained almost the same. From this, he concluded that even heavy substances, like gold, were made up of mostly empty space. Later, when better radiation detectors were developed, Rutherford found that some radiation bounced off the sheets of gold in separate ways. Due to this, he said that almost all of the gold was empty space, but it did contain some very small, solid particles which allowed the radiation to bounce off. Using the information recorded from his experiments, Rutherford was also able to calculate the size of the nucleus, saying it was like a penny in a circle with a radius of 1km (Lewis and Waller, 1986).
Rutherford’s model was later improved by one of his students Neils Bohr, who showed electrons in specific orbits. Development of the model since there have been various developments since Rutherford’s atomic model, to change it to what is looks like today. Neils Bohr, who lived from 1885-1962, was one of Rutherford’s students. He believed that the atom’s nucleus was orbited by electrons in distinct regions or energy levels, introducing the idea of electron shells. James Chadwick, who lived from 1891-1974, was able to show that the nucleus had two particles, positively charged protons, and neutrally charged neutrons. Erwin Schrödinger, in 1926, suggested that electrons moved in waves, rather than set paths, around the nucleus. He believed that it is impossible to know the precise location of the electrons, but rather they exist in ‘clouds of probability’ now known as orbitals (Roberth, 2018). Schrödinger’s model is still widely believed and accepted today as the current most accurate atomic model. Current thinking suggests that electrons do not move like planets, as their orbitals are not round. Electrons rather move in a ‘chaotic’ manner around the atom in distinct areas (Silvester, 2015).
In conclusion, there have been many different models of the atom, which have been improved each time, to produce the model of the atom which is considered most accurate today. Ernest Rutherford performed various scientific experiment to discover what he did about the atom, and whilst his model may not be considered the most correct, he managed to uncover valuable information about the atom and given insightful teaching, that has contributed to every model of the atom since and helped develop the understanding of the current atomic model.
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