The Development of the Dalton Atomic Model
Sonali Purohit
Gateways
2/13/2019
The Development of the Dalton Atomic Model
To understand the technology used to further explore atoms, one must have a firm grasp on what an atom really is. The term "atom" comes from the Greek word for indivisible because it was once thought that atoms were the smallest things in the universe and therefore, could not be divided. However, we now know that atoms are made up of 3 basic things; protons, neutrons, and electrons. Those particles can then be separated even smaller, but most do not tend to look deeper into that unless they are studying nanotech. Atoms are the basic units of matter and the defining structure of elements. Ergo, anything, whether it be living or nonliving, is made of atoms. Due to this, they are considered to be the “building block” of all matter. To look at an example of an atom, look at the periodic table. They are in every single element and play a very significant role in it. To illustrate, carbon has 6 protons and 6 neutrons, these amounts heavily influence the structure of the whole element.
Democritus, a Greek philosopher, is credited with the discovery of the atom. Like any good scientist, he founded a guiding question for his research. “What was to happen if one took an object, and kept breaking it into smaller and smaller pieces?” To put this into perspective, take a tree. If you took a bark of its wood and kept on breaking it, is it still a tree? How long could you keep breaking the bark until there is nothing left? Well, Democritus’s answer was that if you fracturing the bark, it would get to a size that could no longer be broken. This, in Democritus’s eyes, would be the indivisible piece. In Greek, “atomos” is the meaning of indivisible, thus creating the English word “atom”.
Long after, Democritus had passed, came another scientist who theorized about atoms. John Dalton, a 1700-1800 scientist, is the creator of the first completed attempt at describing atoms and their properties in full. Dalton based his theory on two laws: the law of conservation of mass and the law of constant composition.
The law of conservation of mass says that matter is not created or destroyed in a closed system. That means if we have a chemical reaction, the amount of each element must be the same in the starting materials and the products. In summary, new mas will not appear and no mass will disappear. The law of constant composition says that a pure compound will always have the same proportion of the same elements. For example, table salt contains the same proportions of the elements sodium and chlorine no matter how much salt you have or where the salt came from. If we were to combine some sodium metal and chlorine gas—which I wouldn't recommend doing at home—we could make more table salt which will have the same composition. The first part of his theory states that all matter is made of atoms, which are indivisible. Dalton hypothesized that the law of conservation of mass and the law of definite proportions could be explained using the idea of atoms. He proposed that all matter is made of tiny indivisible particles called atoms, which he imagined as "solid, dense, impenetrable, movable particle(s)". It is important to note that since Dalton did not have the necessary instruments to see or otherwise experiment on individual atoms, he did not have any insight into whether they might have any internal structure. We might visualize Dalton's atom as a piece in a molecular modeling kit, where different elements are spheres of different sizes andcolors. While this is a handy model for some applications, we now know that atoms are far from being solid spheres.
His second part of the theory was that all atoms of a given element are identical in mass and properties. Dalton proposed that every single atom of an element, such as gold, is the same as every other atom of that element. He also noted that the atoms of one element differ from the atoms of all other elements. Today, we still know this to be mostly true. A sodium atom is different from a carbon atom. Elements may share some similar boiling points, melting points, and electronegativities, but no two elements have the same exact set of properties. In short, he believed that each chemical element is composed of atoms of a single, unique type, and though they cannot be altered or destroyed by chemical means, they can combine to form more complex structures (chemical compounds).
The third part of Dalton's atomic theory, he proposed that compounds are combinations of two or more different types of atoms. An example of such a compound is table salt. Table salt is a combination of two separate elements with unique physical and chemical properties. The first, sodium, is a highly reactive metal. The second, chlorine, is a toxic gas. When they react, the atoms combine in a 1:1 ratio to form white crystals of NaCl, which we can sprinkle on our food. Since atoms are indivisible, they will always combine in simple whole number ratios. Therefore, it would not make sense to write a formula such asNa0.5Cl0.5 because you can't have half of an atom. In the fourth and final part of Dalton's atomic theory, he suggested that chemical reactions don't destroy or create atoms. They merely rearranged the atoms. Using our salt example again, when sodium combines with chlorine to make salt, both the sodium and chlorine atoms still exist. They simply rearrange to form a new compound.
Although Dalton’s theory was far from the truth about atoms, it provided a strong foothold for the future scientists who theorized about the atomic structure. This allowed them to alter Dalton’s ideas but have a basis to work off of during research. Thanks to Dalton, the atomic structure that we use today was only created because of his commitment to studying it. With the knowledge, we have about atomic structure, many life-saving technology pieces are in pursuit of being created. With any luck, we could apply the information about atomic structure into technology and create automation so small that we could observe the body from the inside and see how the cells of, perhaps a cancerous person, function. This could broaden the ideas of cures that are being brought to the table and explore new medicines that could counteract certain illnesses of the body.
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