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John Dalton and the First Atomic Model
Describes atoms as tiny indivisible particles that have no internal structure. This model has no sub-atomic particles. Through experimental methods, he transformed the idea of the atom into the first scientific theory of the atom. -
J.J. Thompson's Plum Pudding Model
J.J. Thompson discovered the first sub-atomic particle, the electron. He discovered that atoms are made up of + and - material which equals an overall nuetral charge. With the knowledge of the electron, he created the "plum pudding" model of the atom. This model describes the atom as lump of positively charged material with the negatively charged electrons spaced out randomly in it. Thompson used the cathode ray tube for his discovery of the electron. -
Ernest Rutherford's Nuclear Model
Ernest Rutherford set out to test the curent model of the atom at that time. He used the gold foil experiment and discovered some groundbreaking things about the make-up of the atom. Rutherford discovered that the atom is not solid, but is in fact made up of mostly empty space. He determined that most of the mass of the atom, and all of its positive charge is located in what he called the nucleus. The nucleus is in the center of the atom, and the electrons are spaced out randomly around it. -
Neils Bohr's Planetary Model of the Atom
There was one thing about Rutherford's model that just didn't make sense. If the electrons are spaced out around the nucleus, how does the atom keep from collapsing because of the opposite charges that would attract? Neils Bohr determined that the electrons moved in concentric fixed orbits around the nucleus, and that is what keeps the atom from collapsing on itself. -
Erwin Schrodinger's Equation
WIth the developments in the theory of electron movement that were discovered in the early 1900s, there had to be a way to accurately describe what was happening. Schrodinger developed mathemical equations to accurately describe electron movement. From this, the development of the electron cloud model came about. The electron cloud model shows the locations in an atom where electrons are likely to be found. -
The Quantum Mechanical Model
The Quantum Mechanical Model evolved from Bohr's planetary model, and Schrodinger's equations. In this model, electrons are arranged in different levels, or quantums around the nucleus. The electrons, depending on how many there are, occupt different energy levels, starting with the lowest. The levels are like rungs on a ladder, you can be on one level, or the other, but you can never be between the levels.
