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400 BCE
ATOMIC PROPERTIES:
After debating the possibilities of cutting stone in half, until the pieces were too small to see, Democritus discovered certain properties of an atom. He titled them, atomos, and they were in constant movement. The collision of atoms would either combine substance or repel them. From that, he learned that matter was built up in combinations of specific atoms. "Development of the Atomic Theory." Development of the Atomic Theory. N.p., 2007. Web. 01 Oct. 2016. -
400 BCE
SPACE THEORY:
Since the unearthing fact that atoms were in a constant state of motion, that left Democritus to stumble upon another property of the atom. Since movement indicates space for the said atom, that meant there was a void in every atom. A void is empty space that leads to various other solutions in the scientific community. Williams, Matt. "Who Was Democritus? - Universe Today." Universe Today. N.p., 27 July 2016. Web. 01 Oct. 2016. -
400 BCE
LEUCIPPUS' DISCOVERY OF THE ATOM:
Democritus' mentor, Leucippus, was the original scientist to create the concept of the modern day atom. It was believed to be an invisible building block that made up the entire universe. It was considered homogeneous, but they varied in size. If they were nonmetals they'd be the rounded spheres we think of now, but metals would have more rigid edges. This was a very uncommon belief back in 400 BC. Bennet, Linda. "What Democritus Thought." Democritus Model. N.p., 2012. Web. 01 Oct. 2016. -
Period: 400 BCE to
ATOMIC THEORY TIMELINE:
TITLE PICTURE CITATION: Trout, Laura. "Atomic Theory - A Haiku Deck by Laura Trout." Atomic Theory by Laura Trout. N.p., 18 Nov. 2015. Web. 01 Oct. 2016. -
LAW OF CONSERVATION OF MASS:
Antoine Laurent Lavoisier, a chemist, used a chemical reaction to prove that energy is never created nor destroyed. He used Mercury Calx (HgO) and just Hg and O to create a chemical reaction. After the reaction it proved to create the same substance, and the same byproduct. It represented how energy only transfers from different forms, instead of being lost. "Lavoisier and the Law of Conservation of Mass." Lavoisier and the Law of Conservation of Mass. N.p., n.d. Web. 01 Oct. 2016. -
ANTOINE LAVOISIER:
Antoine Lavoisier was the scientist that named the element, Oxygen. He also was the developer of the law of the conservation of mass, which eventually led to an accurate atomic model. The combustion theory was his idea as well, which would show chemical reactions, and energy transfer. "HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom." HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom. N.p., n.d. Web. 02 Oct. 2016. -
DALTON'S ATOMIC THEORY:
John Dalton, who piggybacked off of Democritus' idea of atoms, proved the theories that had been discussed since 400 BC. His atomic theory states that atoms are indestructible, that elements contain atoms with the same mass/properties, and compounds are two or more elements chemically combined. He used the fact that chemical reactions just rearranged the atoms to prove these ideas. It's the basics to chemistry class now. De Leon. "Dalton's Atomic Theory." Dalton's Atomic Theory. N.p., n.d. Web. -
JOHN DALTON:
John Dalton's atomic theory was using the law of conservation of mass, and the law of constant composition. Though, along with that theory, he started to arrange the elements by their atomic weight. He believed that the nucleus held all of the dense mass of the atom, and could be measured. This led to creating the Periodic Table of Elements. Biography.com Editors. "John Dalton Biography." Bio.com. A&E Networks Television, 14 Sept. 2015. Web. 01 Oct. 2016. -
DMITRI MENDELEEV:
Mendeleev was the first chemist to arrange the known elements in a table based on periodicity. He created a very similar chart to The Periodic Table of Elements. He ordered them by increasing atomic mass, trends, and he even left spots for undiscovered elements. Those blank elements had some accurate estimated properties. "HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom." HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom. N.p., n.d. Web. 02 Oct. 2016. -
J.J THOMSON:
J.J Thomson is responsible for the uncovering of the electrons in the scientific community. He experimented with a negatively charged tube, and positively charged neon gas. Through that he found that most elements were neutrally charged, which resulted in the Plum Pudding Model. The raisins were electrons and the dough would be-what is now known as-protons. He didn't, however, discover protons. "Joseph John "J. J." Thomson." Chemical Heritage Foundation. N.p., 2016. Web. 01 Oct. 2016. -
CATHODE RAY TUBE:
The Cathode Ray Tube was a tool used in the Gold Foil Experiment by Rutherford. The tube functions as a vacuum, but different wavelengths would pass through the tube. Depending on the charge of the wave a color would be emitted. From that Rutherford could uncover if atoms were positively or negatively charged. It founded the discovery of electrons. Silsby, Jim. "What Did Ernest Rutherford Use to Detect the Alpha Particles in His Gold Foil Experiment?" Quora. N.p., 11 Aug. 2016. Web. 1 Oct. 2016. -
GOLD FOIL EXPERIMENT
Ernest Rutherford went through an experiment to test the positive and negative charges of radiation as it passes through metal. The metal was golden foil, and there were three different forms of radiation. There were gamma, beta, and alpha rays that go in decreasing order of energy. This eventually lead the way to the discovery of the proton based off the radiation's charge and energy in their magnetic field. "The Gold Foil Experiment." The Gold Foil Experiment. N.p., n.d. Web. 01 Oct. 2016. -
PLUM PUDDING ATOMIC MODEL:
Electrons proved to be lighter than the Hydrogen atom in 1897. So Thomson conducted experiments in order to see the amount of electrons that were in a hydrogen atom. Atoms generally have no charge which meant the thousands of electrons used to make up the mass of the hydrogen atom were not there naturally. That further developed the model of atoms which included e- and p+ to neutralize the charge. "How Did J.J. Thomson Change Dalton's Atomic Theory?" Socratic.org. N.p., 21 Sept. 2016. Web. -
ROBERT MILLIKAN:
Robert Millikan used an oil drop experiment, where he would use charged magnetic fields to determine the force to neutralize gravity. From there he could measure the charge of an electron, and the mass of positive or negative charged atoms. Thus, giving further information about the pieces of atoms. "HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom." HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom. N.p., n.d. Web. 02 Oct. 2016. -
RUTHERFORD MODEL:
This model was the byproduct of the Gold Foil Experiment constructed by Rutherford. It explained that an atom's mass was solely located in a nucleus, which is at the center of an atom. Then, the electrons would orbit around the nucleus within an electron cloud. It gives us the information on the structure of an atom's composition. The Editors of Encyclopædia Britannica. "Rutherford Atomic Model." Encyclopedia Britannica Online. Encyclopedia Britannica, 9 Feb. 2015. Web. 01 Oct. 2016. -
NIELS BOHR:
Based off the breakthroughs during Niels Bohr's lifetime he was able to uncover properties of the pathways of electrons. His main theory was that electrons moved in patterns, but these patterns could be altered. If an electron were to go down an orbit trail, then energy would be released, and if the electrons moved up an orbit then energy would be absorbed. "Niels Bohr - Facts". Nobelprize.org. Nobel Media AB 2014. Web. 2 Oct 2016. -
HENRY MOSELEY:
Henry Moseley was the chemist that produced the modern Periodic Table, that is ordered by atomic number instead of atomic mass. He understood that the elements increased in x-rays linearly as they went down the chart. He reasoned that the positively charged nucleus was to blame, but in his chart he also left spaces for new elements. “Henry Moseley.” Famous Scientists. famousscientists.org. 29 Dec. 2014. Web. 10/2/2016 -
BOHR PLANETARY MODEL:
The Bohr Model, created by Niels Bohr and Ernest Rutherford, depicts an atom in planetary form. The electrons orbit the nucleus in an orderly fashion. It easily represents valence electrons and energy levels, but is flawed from evidence of quantum mechanics. Now, electrons have be known to move wildly within the cloud. They follow probability, instead of patterned function. Helmenstine, Anne Marie. "Review the Bohr Model of the Atom." About.com Education. N.p., 22 July 2016. Web. 01 Oct. 2016. -
ERNEST RUTHERFORD:
Rutherford had many accomplishments with his Gold Foil Experiment, but some of the groundbreaking information that was later discovered was proposed by him. He originally believed that the nucleus of a hydrogen was a proton or positive. He also theorized the existence of neutrons. "HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom." HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom. N.p., n.d. Web. 02 Oct. 2016. -
QUANTUM MECHANICAL MODEL:
Erwin Schrodinger, a well known chemist, created the Quantum Mechanical Model of the atom. It's similar to the Bohr Model, as it portrays where electrons are, but differ greatly. This model uses mathematical equations to predict the probability of where an electron will be in the cloud at any given moment. It's a more accurate depiction of the cloud. G, Molly. "Erwin Schrodinger - 1926." Timeline of the Atom:. N.p., Nov. 2011. Web. 01 Oct. 2016. -
ELECTRON CLOUD MODEL:
This is basically the same model created by Schrodinger, but doesn't focus on the location of the electrons. It simply states that the electrons move all around the electron cloud and nucleus. So, they're not in a systematic orbit, like it was previously thought, but it's not as wild as one would think. They stick to their specific energy levels. "Development of the Atomic Theory." Development of the Atomic Theory. N.p., 2007. Web. 01 Oct. 2016. -
ERWIN SCHRODINGER:
Erwin Schrodinger theorized that radiation would be absorbed by electrons in the cloud depending on their specific location inside of the atoms.His ideas for the energy levels based off the electrons' orbits were formatted in a wave. That meant that he could calculate which waves had the most energy from quantum mechanics. "Erwin Schrödinger - Facts". Nobelprize.org. Nobel Media AB 2014. Web. 2 Oct 2016. -
JAMES CHADWICK:
James Chadwick was a collaborator with Ernest Rutherford, but had multiple discoveries on his own. Chadwick was the founder of the neutron using radiation levels from wavelengths. This then contributed the the process of fission and the atomic bomb, let alone the composition of an atom. "HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom." HISTORICAL OUTLINE of the Atomic Theory and the Structure of the Atom. N.p., n.d. Web. 02 Oct. 2016.
