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The Beginning
*The year is actually in BC but it won't fit
Democritus was a Greek philosopher who came up with the existence of atoms by asking if a piece of matter were to be broken in half, then in half , then in half again, until it was no longer able to be halfed again. Image from: http://www.universetoday.com/60058/democritus-atom/ -
461
Popularity Beats All
*The year is actually 384 BC
The more popular Greek philosopher Aristotle believed that Democritus's theory was ridiculous and dismissed it. With him being very popular at the time, people believed Aristotle and ignored Democritus's Atomic Theory, and the study of the atom was delayed more than 2000 years. Image from: http://www.liberal-vision.org/liberal-philosophy/aristotle-384-322-bce-the-politics/ -
Physics?
English physicist and mathematician Isaac Newton suggested that there was a universe much smaller than ours that had small, solid masses that were always in motion. Image from: http://disabledlives.blogspot.com/2011/01/isaac-newton-1643-1727.html -
Atoms are In
The idea of the existence of atoms is finally studied upon by the English chemist, meteorologist, and physicist John Dalton. Dalton formed his atomic theory which consisted of:
1. Atoms being tiny particles that can be foundd in all matter
2. Atoms in each element were similar and diffrerent from one another
3. Atoms couldn't be made, divided into smaller particles, or destroyed
4. Atoms in two or more elements when combined make compounds
5. Atoms in a chemical reaction can't be destroyed -
Proportional World
Italian scientist Amedeo Avogadro proposed that everything has a ratio, meaning that the volume of a gas is proportional to the number of atoms or molecules regardles of the nature of the gas. Image from: http://www.britannica.com/blogs/2011/07/amedeo-avogadro-law-number-mole/ -
Organization
Credit for the development of the modern periodic table goes mostly to the Russian chemist Dmitri Mendeleev. Interestingly, he did not just organize the elements that were already known at the time, but he also organized the undiscovered ones as well by placing blanks into his chart as a reservation unitl it is discovered. Image from: http://www.biography.com/people/dmitri-mendeleyev-9405465 -
The Good, the Negative, and the Ugly
Joseph John "J.J." Thomson performs his experiment with cathode rays which led to the discovery of the electron, He was able to show that cathode rays were composed of a negatively charged particle that was lighter than the hydrogen atom. Image from: http://ericsaltchemistry.blogspot.com/2010/10/jj-thomsons-experiments-with-cathode.html -
The Positive Part of the Bad and Ugly
Ernest Rutherford, an English physicist, discoverd that alpha particles are postively charged ions with a mass of about 7300 electrons. Image from: http://en.wikipedia.org/wiki/Ernest_Rutherford -
Radioactive Irony
Marie Skłodowska-Curie and her least popular husband Pierre Curie were French scientists and were able to discover radioactivity by studying the decay process of uranium and thorium. Ironically, Marie's death was believed to be from aplastic anemia which is caused by long exposure to radiation. Image from: http://tugpullpushstop.blogspot.com/2013_06_01_archive.html -
HeHe
Frederick Soddy, an Englsih radiochemist, discovered isotopes by showing that uranium decays to radium and also showing that a radioactive element may have more than one atomic mass but still having identical chemical properties. Image from: http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1921/ -
The Gold Foil Experiment
Hans Geiger, one of Rutherford's assistants, had one of his students design an experiment in which a beam of alpha particles was aimed at a sheet of thin gold foil with a zinc sulfide screen surrouding it. It was most expected that the alpha particles would just go straight through the foil, but some were greatly deflected. This made Rutherford reason the existence of a nucleus in an atom. Image from:http://www.rsc.org/chemsoc/timeline/pages/1911.html -
Thinking Outside of the Nucleus
Niels Bohr, a Danish physicist, suggested that electrons exist only in certain energy levels outside the nucleus. Image from: http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html -
How Convenient!
English physicist Henry Gwyn Jefferys Mosely discovered that the atomic number of an element is found by calculating the number of protons within that element. Image from: http://itap-tthv.org/moseley_2012/ -
That's a lot of Isotopes!
British chemist and physicist Francis William Aston won a Nobel Prize in Chemistry for his discovery of identifying 212 isotopes by using a mass spectograph, an analytical technique that produces spectra of the masses of the atoms or molecules comprising a sample of material. Image from: http://www.nndb.com/people/289/000099989/ -
Riding the Waves
French physicist Louise de Broglie suggested that if waves could behave like particles, particles could behave like waves, meaning whether an object acts as a particle or as a wave depends on how the object is observed. Image from: http://www.nndb.com/people/313/000072097/ -
"I am the one who is uncertain!"
Awesomely named German nuclear physicist Werner Heisenberg determined that it is impossible to know both the energy or momentum and the exact position of an electron at the same time. This concept is also known as the Heisenberg uncertainty principle. Image from: http://en.wikipedia.org/wiki/Werner_Heisenberg -
Splitting the Atom
British physicist John Cockcroft and Irish physicist Ernest Walton were able to create the first nuclear reaction by managing to split the nucleus of an atom. Image from: http://beust.com/weblog/2009/07/04/splitting-the-atom-is-hard-splitting-strings-is-even-harder/ -
Antiparticles
Paul Dirac, an English theoretical physicist, proposed the exisistence of antiparticles, particles with with the same mass and opposite charge. Image from: http://en.wikipedia.org/wiki/Paul_Dirac -
Staying Neutral
English physicist Sir James Chadwick discovered another particle in the atom that has a similar weight to that of a proton. It also had a neutral charge and was called a neutron. Image from: http://www.nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html -
Unstable Discovery
From 1941 to 1951, American scientist Glen Theodore Seaborg discovered eight transuranium elements which are elements that have an atomic number greater than 92, unstable, and decay radioactivity into other elements. Image from: http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1951/seaborg-bio.html
