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History of the Atom Part 1: Democritus to DaltonAtoma: meaning "cannot be divided" in Ancient Greek.
The history of the atom is fascinating. If we take a small piece of paper and tear it in half, then tear one of those pieces in half and so on and so on, we will eventually be unable to tear it in half any further. We can then get a magnifying glass, then a microscope, and use progressively finer points and blades to cut the paper, but eventually we will be foiled. If you are a high school science teacher this is a good experiment to do; the kids love it and it's a good introduction to both particles and the microscope.
Democritus
Democritus (460BC to 370BC) was an Ancient Greek philisopher who took this idea and ran with it. To him matter, which is anything with mass, could only be broken down so far and then no further. These particles were called atoma, or "indivisible particles". He thought that atoms were built like little solar systems, with tiny planets orbiting a tiny sun. The majority of his atoms was therefore empty space (void), a feature of his thinking. This excited my imagination when I was a child, imagining worlds within worlds within worlds, entire universes contained in a single blade of grass.
The particle concept went out of fashion for a while; Aristotle proposed "four elements"; earth, wind, fire and water. These were popular for around 2000 years. Eventually problems were encountered with this theory.
Robert BoyleIn the mid to late 1600s a brilliant Irish scientist by the name of Robert Boyle found that none of the supposed "four pure elements" could be extracted from gold, setting the stage for the demise of that theory. He himself dabbled in alchemy so his chemical observations were partially a result of his attempts to transmute base metals into gold. Boyle also had a keen interest in Physics. He discovered that pressure and volume of a gas sample are inversely related (when one goes up, the other goes down). This was also an important step towards the concept of fundamental particles making up matter. His other investigations included the behaviour of sound, light, the nature of colour and more.
Antoine LavoisierLess than a century later a French scientist by the name of Antoine Lavoisier defined what we know as "elements" today; substances that have definite chemical properties. 
Lavoisier (shown to the left) made some unbelievable contributions to our modern ways of thought. He was born into a wealthy family and inherited a fortune when he was very young, effectively allowing him to lead any kind of life he liked. Luckily for us he was interested in the sciences. Some of his outstanding achievements include introducing the metric system, pioneering analytical calculations in chemistry, identifying Hydrogen and Oxygen, investigating combustion and the law of conservation of mass, and much much more.Many of his experiments required a great deal of heat to burn off impurities from or cause reactions in the samples he was working with. In order to do this as efficiently as possible, Lavoisier built a Solar Furnace (pictured below). This is the first example of a heliostat, which is a device used to concentrate sunlight. Antoine Lavoisier was eventually beheaded when the French aristocracy was overthrown in the Revolution of 1789–1799.
John Dalton
After Lavoisier came the Englishman John Dalton. At around 1800 he had proved that substances reacted in definite proportions and these proportions could be predicted for known substances. Through copious experiments Dalton started to assign weights and chemical properties to these definite substances that now bore the name "elements". He also assigned symbols to different elements and proposed chemical structures for some of the compounds he investigated.
The combinations of elements into compounds could only be possible with the concept of the atom at its centre. Each element reacted in a different way; it is chemical properties that define an element. Within a sample of a particular element, all the atoms reacted the same way. John Dalton is rightly recognised as the founder of the modern theory. He died in 1844. |
