PRESENTATION OUTLINE
Democritus/465 BC
Democritus believed that atoms cannot be destroyed, or differ in size,shape, and temperature, are always moving, and are invisible. His theory also stated that there are infinite amount of atoms.Democritus created the first atomic model, his theory was a baseline for future scientist.
Aristotle/384-322 BC
ARISTOTLE DID NOT BELIEVE IN AN ATOMIC THEORY. HE THOUGHT ALL MATERIALS WERE NOT MADE OF ATOMS BUT OF THE FOUR ELEMENTS, EARTH, FIRE, WATER,AIR. HE BELIEVED EVERY MATERIAL ON EARTH IS MADE OF SMALL AMOUNTS OF THESE ELEMENTS. HE DID NOT BELIEVE IN DEMOCRITUS THEORY OF ATOMS. THIS CAUSED PEOPLE TO OVERLOOK THE IDEA.
John Dalton/1803
Dalton used the study of meterology to create his view of the atom. He came up with the Five Atomic Theory Principals:
1: All matter is comprised of atoms
2: All atoms of an element are identical in every way
3: Atoms of different elements are different
4: Atoms of different elements combine to form compounds
5: Atoms cant be created or destroyed during ordinary chemical reactions
J.J Thomson/1897
In 1897 he discovered the electron.(a negatively charged particle). He belived that an atom was made up of many electrons and that equaled the atomic mass.Thats when he realized that an atom would have a very high negative eletric charge, which meant it had to balance with a positive charge. Thomson notcied that previous atomic models did not include this and that was when he created his model which resembled plum pudding.
Ernest Rutherford/1898
Rutherford was a student of Thomson at Cambridge university. Together, they studied x-rays. They studied the effects of xrays on the conductivity of gas. Those studys were the results of dividing of atoms and molecules into ions. He conducted a study with foil which resulted in two radiation types, "alpha" and "beta". Alpha was the nucleus of a helium atom, while beta was the electron. The Geiger-Marsden experiment was his experiment that helped him discover the structure of an atom
Max Planck/1900
Max Planck studied previous studies by Ernest Rutherford about radiation. His work on thermodynamics led to his quantum theory. His theory is that energy is radiated in packets rather in an unbroken wave, this explains the colors of hot glowing matter. These packets are called quanta and was able to determine the energy of eah quanta by using his own formula called Planck's constant.
Robert Millikan/1909
Millikan conducted an experiment that measured the charge of an electron. He studied each droplet from his experiement and concluded that the charge of a drop was a finite value. This confirmed J.J Thomson's previous hypothesis. The mass of an electron is at least 1,000 times smaller than the lightest atom.
Niels Bohr/1922
He discovered that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. He created the liquid drop theory that suggests that a single droplet is an represenation of a nucleus. He also contributed to the quantam theory. Which states that an electron can be viewed in two ways, either as a particle or as a wave
Erwin Schrödinger/1926
Schrödinger took Bohr's atomic model a step further. He used mathematical equations to predict the location of electrons. His model is known as the quantam mechanical model. His model does not tell you the exact location of the electron. His model shows the electron as clouds surrounding the nucleus, this introduced sub-energy levels.
James Chadwick/1932
In 1932 he proved the existence of neutrons.(particles devoid of any electrical charge.) Neutrons differ from alphas. He used his nuclear transformation to show that in a reaction a neautral particle with the same mass as a proton was emitted. Ernest Rutherford hadearlier proposed that such a thing existed
Modern day atomic model
Today we now know that electrons are in constant movement around the nucleus.Protons and neutrons are within the nucleus and quarks are within protons and neutrons.
