Evolution of the Atomic Structure

By: Madison Strauch

Democritus (400 BC)

Democritus came up with the concept of the atom. He and other scientists who began to study atoms perceived atoms as indivisible. He thought that things were solid based on the shape and size of the atom that made of the object, and that everything was made up of different atom patterns or combinations. He figured this out by believing that if you cut an object enough times over and over again you would reach an atom.

Aristotle (400 BC)

He disagreed with Democritus. He said that nothing was made up of atoms or smaller things. He said that everything was made up of four elements. He wasn't disproved till the 17th century.
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Newton (1704)

Newton suggested that atoms in things could be moved. Also that atoms were a type of living things swimming around in gases. He also introduced the idea of attraction that keep atoms together, Atomic forces.

Dalton (1803)

He figured that every form of matter was entirely made up of smaller particles. He wrote about atomic weights. Dalton said that different elements could be differentiated based on their different atomic weights. He also thought that molecules of an element are certainly made up of atoms with the same proportions, with water being the only exception. These theories were made up by his work with gasses and his observation of particles.

Mendeleev (1869)

Mendeleev is mostly know for this work with the Periodic table and Periodic Law. Periodic Law states that the properties of elements reappear as the atomic numbers increase as the atomic numbers increase of the table.

Thompson (1904)

Thompson discovered the electron. He said that an atom was a positively charged sphere with negative electrons in it. He also said that the negative and positive charges of the electrons and protons were equal. This created a neutrally charged atom.

Rutherford (1911)

Rutherford challenged Thompson's idea. The idea that there was an equal amount of electrons as protons. He did an experiment where he shot atoms at a thin gold sheet. If they are equal that would go through instead of bouncing off of the sheet. Many atoms did bounce of the sheet. This experiment suggested that there weren't as many protons as electrons. Also that they had a positively charged nucleus.
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Moseley (1913)

Moseley measured X-ray spectral waves of a few elements in order to arrange the elements by atomic number. He wanted to do this so it was instead of atomic mass, which allowed the elements to be arranged by "families". X-ray spectral waves are waves that elements give off when they are put under an increase in energy.

Millikan (1917)

Millikan discovered the way to measure the charge of an electron. He was able to prove they had a small finite charge. He used the Oil Drop Experiment. Old drops would be sprayed into a chamber. Some of them would fall into a pinhole, then looked up a microscope. Then the air is the chamber was ionized and the droplets that didn't capture an electron fell to the bottom of the chamber. This proved that electrons had a small finite charge.
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Bohr (1922)

Bohr suggested that electrons orbit in different levels of the nucleus. Rather than unorganized and floating everywhere. Bohr proved Rutherford wrong because if the electrons wer that unstable they would have spiraled in the the nucleus. Bohr said the levels have some restraint the them so they works with the movement of the electrons.

Louis de Broglie (1924)

He specialized in theoretical physics. Specifically problems involving quanta. Quantum is the minimum amount of any physical entity involved in an interaction (Wikipedia). His ideas helped develop the wave mechanics theory.

Aston (1922)

He discovered a lot of isotopes. Isotopes are atoms form the same element that differ in mass.) He used a mass spectrometer. A spectrometer is a device that help identify the amount and type of chemicals in the sample.
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Gerd Binnig

Invented the scanning tunneling microscope. That is an instrument for looking at surfaces at an atomic level.