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460
DEMOCRITUS THE IDEA OF THE ATOM
460 BC
Democritus developed the idea of the atom. He asked the question “If you break a piece of matter in half, how long till it cannot be broken down anymore.” he thought it had to end at some point. He called these matter particles Atoms. However, Aristotle dismissed the idea as worthless. -
Period: 460 to
Atomic Theory
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ANTOINE LAVOISIER'S ATOMIC THEORY
The famous chemist from France; mostly known for very carefully weighing all chemical experiments. 2 factors he founded: 1) the simplest substances, which he called elements, could not be broken down any further and, 2) these elements always reacted with each other in same proportions. He combined oxygen and hydrogen, which makes water. -
ENGLISH CHEMIST JOHN DALTON
English chemist John Dalton performed experiments with various chemicals. They showed that matter consisted of basic particles (atoms). He didn’t know what they were but knew that they were important. -
JJ THOMPSON DISCOVERS THE ELECTRON
JJ Thomson discovered the electron and makes a model for an atom. He knew that the electrons were a negative charge and something had to be positive. -
ROBERT MILLIKAN'S DISCOVERY
Millkan's earliest success was the accurate determination of the charge carried by an electron, using the famous "falling-drop method." So his work was based off of what J.J. Thomson discovered about electrons in 1898. -
ERNEST RUTHERFORD'S ATOMIC DISCOVERY
Rutherford published his atomic theory discribing the atom as having a central nucleus (positive) surrounded by negative orbiting electrons. He found this out by doing an experiment with his gold foil model which contained a detecting screen (acting as the membrane), particle emitter, and silt. This model suggested that most of the mass in an atom was contained in a small nucleus. -
NIELS BOHR'S ATOMIC THEORY AND MODEL
Bohr applied the quantum theory to Rutherford's atomic structure by assuming that all electrons travel in stationary orbits defined by their momentum. This led to possible energy levels for their orbits. Bohr also developed his very own model of what an atom would look like with the nucleus and the electron lines. It is called the Bohr Model. -
LOUIS DE BROGLIE
French quantum physicist Louis de Broglie introduced his theory of particle-wave duality in 1924. In his time, the wave and particle interpretations of light and matter were seen as being at odds with one another, but de Broglie suggested that these seemingly different characteristics were instead the same behavior observed from different perspectives — that particles can behave like waves, and waves (radiation) can behave like particles. It was originally written as his doctoral thesis, but his -
WERNER HEISENBERG'S THEORY
Heisenberg is best known for his theory of quantum mechanics when he was only 23 years old. His theory is based off of what we can only see, which would be the radiation emitted by the atom. Most of his work was associated with Niels Bohr. SO he was big on the electron deal; he stated that "We cannot always assign to an electron a position in space at a given time, nor follow it in its orbit." -
ERWIN SCHRODINGER
Schrodinger laid the foundation of the wave-mechanics approach to the quantum theory, which was based of Max Planck. He also put his now-famous equation out for the world to see. His theory was based off of energy levels in the atom. -
CHADWICK'S NEUTRAL DISCOVERY
James Chadwick discovered the neutrally-charged neutron. After a decade long struggle, Chadwick did a test on Beryllium and bombarded the element with alpha particles. This caused some of the protons to be discharged, creating neutrons. -
Atomic Theory
Atomic Theory Scientific theory of the nature of matter, states matter is composed of atoms.
