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460 BCE
Democritus's
Democritus was the first person to think of an atom. He believed that they were invisible and indivisible. He thought that different objects were just different configurations and combinations of atoms. HE thought that haveing water atoms being smooth rolling over each other freely but a solid being rigid would hook together. -
384 BCE
Aristotle
Aristotle developed the Idea of five different elements that made up the universe. Air, earth, fire, water, and aether. He believed that all matter is either made of these four elements or combinations of them. (excluding aether which he believed stars and planets were made of.) -
John Dalton
John Dalton thought that atoms of different elements have different sizes and mass and chemical mixtures and atoms of the same element are completely and absolutely the same. Another point from his theory states that chemical reactions are just a rearrangement of atoms. -
J.J Thomson
J.J Thomson was the first person to discover the electron. A smaller substance that look like they are placed inside the atom around in his diagram for the atom. He believed that the whole thing was positively charged except for the electrons this was later disproved -
Ernest Rutherford
Ernest Rutherford discovered that atoms actually had lots of space between the nucleus and the electrons unlike Thompson's plum pudding model where they were supposedly place inside the atom. He discovered this by shooting positively charged alpha particles at a thin sheet of gold foil with glow in the dark sheets all around it. some reflected off and some went strait through the foil. This also led to the discovery of the hard inner area called the nucleus. -
Niels Bohr
He thought of the atom as a small, positively charged nucleus surrounded by electrons. He also discovered that electrons travel in separate orbits and the different number of electrons determines the properties of the element. -
Erwin Schrodinger
Erwin Schrodinger and with the help of Werner Heisenberg together they determined the regions in which an electron would most likely be found. They found this out by using mathematical equations for the behaviour of the waves. -
Werner Heisenberg
Werner Heisenberg developed the uncertainty principle. It states that you can't measure the velocity and position of an electron and yet both separately. He also discovered that there were neutrons and protons inside the nucleus.
