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460
Democritus
300 BC
Believed everything in the world was made up of atoms. -
Antoine Lavoisier
He is known as the father of modern chemistry and clarified the concept of an element as a simple substance that could not be broken down by any know mthod of chemical analysis. He also devised a theory of the formation of chemical compounds from elements. -
Law of Conservation of Mass
A law that states that mass is neither created or destroyed in ordinary chemical and physical changes. -
Dalton's Atomic Theory
1) All matter is made of atoms. Atoms are indivisible and indestrucatable.
2) All atoms of a given element are identical in mass and in properties.
3) Compounds are formed by a combination of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement of atoms. -
John Dalton
1) All matter is made of atoms. Atoms are indivisible and indestrucatable.
2) All atoms of a given element are identical in mass and in properties.
3) Compounds are formed by a combination of two or more different kinds of atoms.
4) A chemical reaction is a rearrangement of -
Dmitri Mendeleev
Mendeleev arranged 63 elements into the periodic table by their atomic weights and organized them into groups that all posessed the same qualities. where there was a gap, he predicted new elements would be found. -
Cathode Ray Tube
Invented in 1897 and is a vacuum tube in which a hot cathode emits a beam of electrons that pass through a high voltage anode and are focused or deflected before hitting a phosphrent screen. -
JJ Thomson
Discovered the electron. -
Plum Pudding Atomic Model
JJ Thomson proposes that the negatively charged electrons he had recently discovered were scattered throughout a positively charged cloud. -
Robert Millikan
Determined the unit charge of the electron with his oil drop experiment at the university of Chicago. -
Gold Foil Experiment
An experiment that positively charged alpha were fired at a thin sheet of foil. Most particles went throughm otheres bounced off at an angle, others were deflected. -
Ernest Rutherford
Hypothesized that an atom consisted of a nucleus that contained almost all the mass of the atom and had a postiive charge. The electrons had little mass and negative charge and they orbitted around the nucleus at a distance. -
Neils Bohr
Neils Bohr applied the quantum theory to Rutherford's atomic structure by assuming that electrons travel in stationary orbits defined by their angular momentum. -
Henry Moseley
Henry Moseley ordered the elements by X-ray spectra, creating the periodic table and making more accurate positioning of the elements. -
Bohr Planetary Model
The neutrons and protons occupy a dense central region called the nucleus and the electrons orbit the nucleus much like planets orbiting the sun. -
James Chadwick
Developed a theory on the atoms and authorized the existence of a neutron, a non-charged particle within the atom's nucleus. -
Quantum Mechanical Model
Erwin Schrodinger made this based to the quantum theory (matter also had properties associated with waves), it uses complex shapes of orbitals and volumes of space in which there is likely to be an electron. It is based on probability rather than certainty. -
Rutherford Model
Came up with the gold foil experiment and watched the reactions of alpha particles. -
Erwin Shrodinger
His wave equation was the second theoretical explinationfor the movement of electrons in a atom.
