Will I Ever See the Carbon Atom Again
The idea of the atom equally the smallest, indivisible unit of measurement of thing has a long history that predates John Dalton by millennia, but his scientifically reasoned theory at the showtime of the 19th century was a ground-breaking evolution in our understanding of this key element of the physical world.
The Origins of the Atom
The idea of an indivisible unit of matter from which all things are made can be plant in texts from both aboriginal Greece and ancient India, but the atom as we know it really got its showtime in ancient Hellenic republic in the sixth century BCE.
The term atom is derived from the word atomos, coined past the aboriginal Greek philosopher Leucippus and his student Democritus around the sixth or 5th century BCE. Literally meaning 'uncuttable', Democritus, in item, spread the idea of the atomos as being infinite in number, eternal, and uncreated physical particles that brand up all matter.
The ideas of the early atomists--as Leucippus, Democritus, and Epicurus are sometimes called--essentialized the concept that the only real change in the world was that of identify--specifically the change in the state of motion or of rest--and that nothing new was always created and that nothing extant ever ceased to exist.
When a person was born, the atomos from which they were composed changed position to make that person what they were. Growth was merely more atomos irresolute position to join an already existing drove of atomos. When someone died and their bodies rust-covered, the atomos but separated and dispersed, and those atomos could be reconfigured afterward to form a bract of grass or a river. They were essentially the Carl Sagans of their day, reminding all of u.s. that we are all made of star-stuff.
This ends up being closer to the bodily reality of thing than the ideas of Democritus' arch-nemesis, Plato, who conceptualized the world being build out of transcendent triangles and polyhedra which gave rise to one of the four elements--World, Current of air, Burn, and Water. These elements would then combine to make imperfect, physical copies of abstracted, perfect forms of any given thing.
Democritus' work survived the autumn of Rome and rode out the European Eye Ages in the Islamic world. The rediscovery of the atomos in Europe came along thanks to the reintroduction of Aristotle, Plato'south pupil who debated the competing ideas of the atomos and Plato's triangles in his ain works, and the Roman poet Lucretius, who wrote of Epicurus' atomist ideas, which built on Democritus' ideas from a couple of centuries earlier.
The reintroduction of pagan philosophy got the governing Church authorities quite aptitude out of shape, though Aristotle at to the lowest degree had the benefit of a monotheistic-ish philosophy that proponents could--and did--fence demonstrated that Aristotle was actually talking near the Abrahamic god, he had only never heard of him so didn't know what name to requite his Prime number Mover.
Epicurus and Democritus, all the same, had no such defense. The atomos meant that no gods were needed to explain life and death, or how forest burns to smoke and ash, or how water and soil turns into crops. Everything could be explained by a change in the position of the various atomos in relation to ane another. The materialist basis for the philosophies of Epicurus and Democritus directly contradicted Church building teachings and so the fruits of that philosophy, the atomos, were branded as foolish pagan heresy, making it dangerous to abet for such a material model.
Even so, there was no getting around the fact that the atomos was a really good way to explain natural phenomenon, so the thought of the atomos stuck around, fifty-fifty being taken upwardly by some within the church who argued that cipher in the scriptures precluded God from creating the universe out of atomos. By the time of the Enlightenment, knowledge of the atomos was adequately widespread amidst the new scientific class but information technology remained a purely philosophical idea, mostly.
John Dalton's Work on Gases
At the turn of the 19th century, John Dalton was an English language pharmacist, physicist, and meteorologist working as a secretary of the Manchester Literary and Philosophical Society. Past 1800, chemistry had undergone one of the nearly dramatic intellectual revolutions in millennia equally scientific rigor began beingness applied to the aboriginal study of alchemy, which came to be called the Chemic Revolution of the 18th century.
While the ancient Greek idea that water, air, fire, and earth were the essential elements of all thing was still taken equally a given by many at the time, chemists similar Antoine Lavoisier laid much of the groundwork for modernistic chemical science during the 18th century by isolating and identifying some of the well-nigh important elements in chemistry, such every bit hydrogen and oxygen. Even so, this scientific understanding of chemistry and the atom at the middle of it all was all the same in its infancy by the time John Dalton inherited it at the starting time of the 19th century.
The properties of gases were of particular interest to Dalton and much of his most of import work revolves around their report. Starting in 1800, Dalton began recording the different pressures of different forms of vapor, which at the time was considered a carve up substance from atmospheric air. According to Universe Today:
[b]ased on his observations of six different liquids, Dalton concluded that the variation of vapor pressure level for all liquids was equivalent, for the same variation of temperature, and the same vapor of any given pressure level.
He also concluded that all rubberband fluids under the same force per unit area expand equally when estrus is practical. Further, he observed that for any given expansion of mercury (i.eastward. noted rise in temperature using a mercury thermometer), that the corresponding expansion of air is proportionally less, the higher the temperature goes.
This became the basis [of] Dalton'south Law (aka. Dalton'due south law of partial pressures), which stated that in a mixture of non-reacting gases, the full pressure exerted is equal to the sum of the partial pressures of the individual gases.
It was during this work on the backdrop of these gases that Dalton noticed a peculiar tendency. He found that certain gases could only be combined in specific ratios to form certain compounds, even when two different compounds shared an element or elements in common.
Dalton began to deduce that if a compound could only be made with specific proportions of component elements, the only manner this could work is if individual units of the component elements were combining discretely in the mixture at a specific ratio to requite rising to i compound and not another.
He further concluded that if two elements can produce two or more than compounds, the manner carbon and oxygen can make both carbon monoxide and carbon dioxide, the ratio of the second chemical element'due south masses given a fixed mass of the first element would inevitably be reducible to modest whole numbers.
Substantially, if calculation a certain amount of oxygen to carbon gives you carbon monoxide, getting carbon dioxide requires adding a multiple of the amount of oxygen used to produce the carbon monoxide, which in this instance would mean y'all'd need to add together twice as much oxygen to get carbon dioxide as you lot needed to get carbon monoxide.
Over again, the only style this could be the case is if the concrete carbon and oxygen substances you were combining were a collection of individual carbon and oxygen units that would individually couple together in specific ratios co-ordinate to the amount of each element present.
These two insights, combined with laws on the conservation of mass and of definite proportions--discovered past Lavoisier and Joseph Louis Proust, respectively--were the essential link between the ancient Greek atomos of Democritus and modern chemistry. Dalton recognized this history, so he called these elemental units atoms.
Dalton'south Atomic Model
Proposing what would come to exist known as the Dalton Diminutive Model, Dalton described five essential backdrop of the atom.
First, every element tin can exist reduced to a single, indivisible unit of itself.
2nd, every atom of an element is identical to every other cantlet of that chemical element.
Third, atoms of different elements were distinguishable by their diminutive weights.
Fourth, individual atoms of one element combine with individual atoms of another element to grade compounds.
Fifth, no atom can ever exist destroyed or created in a chemical process, only the arrangement of atoms changes.
While some of these would turn out to non be entirely correct--isotopes of an element, for instance, tin can differ from 1 another and fifty-fifty have dissimilar properties while all the same existence classified as the same chemical element--what Dalton described at the start of the 19th century is pretty close to our agreement of matter on the macro level today.
How Dalton'south Diminutive Model was Refined
Over the next century, Dalton'southward Atomic Model would be refined every bit further experimentation showed that the atom wasn't as neat and tidy as Dalton first proposed. Marie and Pierre Curie discovered that atoms of sure elements released radiation, which they could non exercise if they were the irreducible fabric that Dalton described.
Later, it would be found that atoms could take an electromagnetic charge, either positive or negative, which nosotros telephone call ions. These ions betoken that normally-neutral atoms must exist fabricated up of a negatively-charged substance straight proportional to a positively-charged substance and then that these two charges canceled each other out. Ions could only be explained if this residual was disrupted, which meant that the electromagnetically charged substances of the atom had to exist distinct and separable. The cantlet, and then, wasn't as modest equally information technology gets.
From there, we got the proton, the neutron, and the electron; the photon and the Planck constant; and Albert Einstein, Niels Bohr, and others unraveling what by now was the heavily revised atomic model of John Dalton and introducing the bizarre earth of quantum mechanics. From there, scientific discipline leaves the orderly and measurable diminutive construction, besides as physics, behind--though no word all the same on whether Plato was right about those triangles.
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Source: https://interestingengineering.com/the-origin-and-development-of-john-daltons-atomic-model-of-matter
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