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400
(460 B.C.-370B.C.), Democritus
This Greek philosopher developed the first atomic theory. He came up with the name "atom" because if you kept on dividing matter into smaller and smaller pieces it will become tiny, indestructible particles which is an atom. -
Period: 400 to
Atomic Model
History -
Dalton
Dalton transfprmed Democritus's ideas on atoms into a scientific theory. He sees atoms as tiny, indestructible particles that have no internal structure. His model is like a tiny, solid sphere. -
Cathode Ray
William Crookes studied the green glow more and found that rays traveled the cathode and hit the ened of the tube, he called the rays "cathode rays", -
Thomson
He is a British scientist that discovered the electron. He sees electrons in a sphere of positive electrical charge. It is known as his "plumpudding model" -
Cathode Ray Experiment
Thomson obsevered the beam of light in the cathode ray tube. He saw and knew that it positve charge attract while negative charge repels. His guess wa rays have small negative charged particles. Then he concluded and discovered electrons are part of the atoms. -
Hantaro Nagaoka
He is a Japanese physicist. He suggested that and atom has a cental nucleus with elelctrons moving around it, just like rings around saturn. -
Rutherford
He is a New Zealand physicist. He discovers that an atom has a positve region which he called "nucleus", with electorns orbiting around it and the rest of the atom is mostly empty space. It failed explaing chemical properties of elements. His model is known as the nuclear atom. -
Rutherford's Gold-Foil Experiment
This is a test of the theory of atomic structure done by him and his coworkers. They shot a beam of alpha particles at the gold foil that was surrounded by fluorescent screen. They thought protons were spread out in the gold atoms and predicted that the particles will pass easily through the fold with little deflection. But instead it passed with none and bounced back. -
Bohr
Niels Bohr states that electrons travel in a circular orbit at a specific place from the nuclues with a set size and energy. Each electron has a fixed energy level thats related to its size. When an electron moves it gains or loses energy. -
Oil Drop Experiment
Robert Milikan did this. This succesful experiment detected and measured the individual subatomic particle. It demostrated the atomic structure of electricity. It determined the mass and charge of an electron. -
Aston
Using the mass spectograph, he disscovered the existence of isotopes. -
Louis de Brogile
He is a French physicist. Louis said that electrons could act as both particles and waves, like light because he found that light waves behave like particles and particles behave like waves. -
Erwin Schrodinger
He is an Austrian physicist that develps mathematical equations to describe where an electron is likely to be found, not its exact location. This leads to the electron cloud model, he uses the this model to find the probability of where an electron may be. The Quantum Mechanical Model is like this. -
James Chadwick
He is an English physicist. James discover the neutron that has no charge. It is inside the atomic nuclei with protons. -
Atomic Bomb
One of the bombings was on Nagasaki, Japan. Two nuclear weapons were used. It was the uranium and plutonium. These two bombings was very big causing thousands of deaths. Atomic bobms are deadly and very humongous. -
Carbon Dating
This is a method of determining the age of biological artifacts that are up to 50,000 years old. It is created from nitrogen and formed by suns radiation that collides with atoms in the atmosphere. That creates these rays in the form of neutrons. and that collides with nitrogen-14 which creates carbon-14,
