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John Dalton
Dalton made up an atomic theory that consisted of four postulates. His theory stated that elements are composed of indivisible particles called atoms. But, his theory is different from the rest because his goes into atoms of different types of elements. Part of Dalton’s theory was incorrect, so that was a minor slip up of his. As stated above, atoms were considered indivisible particles, but now they are known to be divisible, made up of protons, neutrons, and electrons. This was a big shock to -
Eugene Goldstein
Goldstein witnessed while working with “cathode rays and the electrical charges of the particle moving through a discharge tube.” (Taken from website, don’t know how to reword it). He noticed that the negatively charged particles moved towards the positively charged end. He also noticed that there were rays moving in the opposite direction, so he named them “Canal Rays”. This led to the discovery of the proton. -
J.J. Thomson
Thomson discovered corpuscles, or electrons as we know them now. Thomas shot a ray filled with charged particles through the cathode ray tube. (Cathode is “negatively charged end, anode is “positively charged end”) The ray then deflected off one of the negatively charged plates to one of the positively charged plates. -
Dmitri Mendeleev
Mendeleev was the first man to make the periodic table, sorting each element by atomic mass. He also proposed the periodic law. There were still holes in the periodic table because there, of course, were still 55 unfound elements by 1869. -
R.A. Millikan
Millikan discovered the actual charge and weight of electrons. He performed an experiment called the “Oil Drop” experiment. He sprayed oil drops into a container, waited till they got to their terminal velocity. He then measured them and figured out their mass. He then filled the same chamber with x-rays, which caused the particles to lose their electrons. After all that, he made a magnetic field in the chamber, and this caused the oil droplets to be suspended in mid-air from friction. He was no -
Ernest Rutherford
Rutherford performed the Gold-Foil experiment, and he was the one who discovered that atom’s are mostly empty, but has a nucleus, which is the only solid part about it. Rutherford made an experiment that involved a gold foil sheet, zinc sulfide, and alpha rays. Rutherford would shoot the alpha rays at the gold foil sheet, which had zinc sulfide surrounding it, so when the zinc sulfide lit up, it led Rutherford to believe that atoms were hollow. -
Neils Bohr
Bohr wanted to answer the quickly rising question of the location of electrons. He discovered that electrons only moved in a circular path, so they were called “Orbits”, and they move around the nucleus. He found out that the electrons have a fixed energy level, and they move from orbit to orbit when they lose or gain energy. He also discovered that the levels are not even and electrons cannot be between levels. Each level also has a maximum number of electrons. -
Henry Moseley
He discovered that the energy the x-rays increased with a linear fashion. He quickly proposed that there was a relationship, and the relationship was a positive charge on the nucleus. This actually re-arranged the table of elements using atomic numbers, instead of the old way with the numbers being re-arranged by atomic mass. Unfortunately, this left holes in the table of elements, but the holes were soon filled with new elements. -
Louis de Broglie
Broglie was trying to figure out of particles of matter could move in a wave, the same way that light behaves as waves and particles. Broglie came up with an equation that showed that particles of matter behave as waves, but not always. This was very uncommon and unknown back then because to them, waves were always waves and particles were always particles. The equation that Broglie used was λ=h/p, with the λ as the wavelength, the h as the Planck’s constant, and the p as the mass times velocity -
Erwin Schrodinger
Schrodinger proved that atoms moved in a wave-like pattern, even though they had a small bit of solid in them. (the nucleus). Schrodinger discovered that there are 4 levels of wave movement with atoms. The levels are “S level, P level, D level, and F level”. The S level has atoms that are spherically shaped, and only have 2 atoms on it at a time. P level has atoms that are dumbbell shaped, and can have up to 6 atoms on it at a time. D level and F level are slightly the same. D level can have up -
James Chadwick
Chadwick discovered the neutron. He, and everyone else in the world, were wondering what else made up the nucleus of an atom? He quickly figured out that there was no electric charge in a neutron. It accounted for the missing weight in the nucleus, and it made the atom a whole
