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John Dalton Was Born
John Dalton was born in Manchester, England. -
Law of Mass Conservation
The Law of Mass Conservation was made by Antoine Lavoisier and was used for Dalton's discovery of the atom. -
Law of Constant Composition
The Law of Constant Composition was made by Joseph Proust and was used for Dalton's discovery of the atom. -
John Dalton Defines the Atom
In 1803, John Dalton found that matter is composed of tiny invisible particles called atoms. His theory was that all atoms of a material are the same, but different materials are made of different atoms. He did not perform any experiments for his discoveries; instead, he used the "Law of Mass Conservation" and the "Law of Constant Composition." The picture shown is what Dalton thought the atom looked like. -
John Dalton Dies
John Dalton died at the age of 77.
He died in Manchester, England. -
JJ Thomson Was Born
JJ Thomson was born in Cheetham Hill, United Kingdom. -
Robert Millikan Was Born
Robert Millikan was born in Morrison, Illinois. -
Earnest Rutherford Was Born
Earnest Rutherford was born in Nelson, New Zealand -
Niels Bohr Was Born
Niels Bohr was born is Copenhagen, Denmark. -
Erwin Schrodinger Was Born
Erwin Schrodinger was born in Vienna, Austria. -
James Chadwick Was Born
James Chadwick was born in Manchester, England. -
JJ Thomson Performs Cathode Ray Tube Expirement
JJ Thomson had a Cathode Ray tube, and he found that when he had a magnetic force on the ray, it would either attract the ray or repel the ray. He discovered the electron and found the first sub-atomic particle from this information. The size of an electron is 1/2000 of a hydrogen atom, which was what people thought the smallest unit in the world was. -
JJ Thomson Creates "Plum Pudding" Model
After his famous cathode ray experiment, JJ Thomson developed the "Plum Pudding" model in 1904. He thought the atom was full of positive charge except for tiny negatively charged electrons inside the positively charged sphere. He found from his works that the atom had an equal amount of negative and positive charge. -
Robert Millikan Performs Oil Drop Experiment
In 1909, Robert Millikan performed his famous oil drop experiment. The experiment had two plates; the top had a small hole and was positively charged. The bottom plate was negatively charged. When Robert sprayed oil mist over the top plate, the atoms would slowly fall. He then sent in X-rays into the particles. Using the rate at which the particles fell, he calculated the charge of an electron, which was 1.60 x 10^-19 C. -
Earnest Rutherford Performs Gold Foil Experiment
In 1911, Earnest Rutherford set up a sheet of gold foil in front of a beam of alpha particles. He found that most rays passed through the foil, but a tiny amount bounced back. From this, he could tell that the alpha particles were hitting the atom's nucleus. Before the experiment, it was unknown that the atom had a positively charged nucleus, as it was thought that the entire atom was positive with negatively charged electrons embedded in it. -
Earnest Rutherford Creates the "Nuclear" Model
After performing his famous gold foil experiment, he was able to find that the atom was not full, but that there was a small positive nucleus within it. He found that the atom was actually mostly empty space. Before his new atom model, scientists thought that charge was spread throughout the atom. -
Niels Bohr Creates the "Planetary" Model
In 1913, Niels Bohr created the planetary model. The previous atomic model could not explain certain attributes of the atom, like fluorescent light. His new model explained how electrons can jump energy levels. His atomic model stated that electrons move in a planetary orbit around the nucleus, and when electron particles become excited, they can change energy levels. His model didn't come from experiments but from Earnest Rutherford's previous ideas about the atom. -
Erwin Schrodinger Creates the Quantum Mechanical model
In 1926, Erwin Schrodinger created the Quantum Mechanical model, which is still used today. Schrodinger found that electrons do not move in a planetary orbit but instead occupy orbitals. He discovered that each of these orbitals could not have more than 2 electrons. Schrodinger made his atomic model by calculating his equation called the Schrödinger Equation. -
James Chadwick Discovers the Neutron
From Chadwick's famous experiment, he found that the nucleus didn't just consist of protons but also neutrons. Rutherford, in his model, was unable to discover the reason why there was extra mass in the nucleus. Rutherford had a theory about protons and electrons mixing, but Chadwick solved the issue with the newly discovered neutron. -
James Chadwick Performs Experiment with Beryllium
In 1932, James Chadwick performed an experiment where he bombarded alpha particles with beryllium where the alpha particles turned to neutrons. These neutrons went into Paraffin wax where they turned into protons and were detected. -
Earnest Rutherford Dies
Earnest Rutherford died at the age of 66.
He died in Cambridge, United Kingdom. -
JJ Thomson Dies
JJ Thomson died at the age of 83.
He died in Cambridge, United Kingdom. -
Robert Millikan Dies
Robert Millikan died at the age of 85.
He died in San Marino, CA. -
Erwin Schrodinger Dies
Erwin Schrodinger died at the age of 77.
He died in Vienna, Austria. -
Niels Bohr Dies
Niels Bohr died at the age of 77.
He died in Copenhagen, Denmark. -
James Chadwick Dies
James Chadwick died at the age of 82.
He died in Cambridge, United Kingdom.