Atomic Theory By: Emmanuel Balderas, Juan Bahena, Justin Kani-Yeboah, Hank Wilkerson
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400 BCE
Democritos
In 440 b.c.e. Democritos came up with the idea that something can't be cut for ever. He called this things “atomos” which means uncuttable. He also said that they were made by different sizes and shapes. However scientist at the time disagree with his statement because, Aristotle a really popular and influential scientist at the time had come up with the idea that this had to do with the elements of the earth, water, fire. -
John Dalton
. In 1808 John Dalton proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass.All matter is made of atoms. Atoms are indivisible and indestructible. Compounds are formed by a combination of two or more different kinds of aatoms. -
J.J. Thomas
J.J Thomas - In 1894, Thomson began studying cathode rays, which are glowing beams of light that follow an electrical discharge in a high-vacuum tube. It Showed that rays were deflected toward a positively charged plate and away from a negatively charged plate. He concluded that cathode rays must be negative. He discovered that there was actually a particle smaller than an atom and he named the new particle an electron. -
Earnest Rutherford
In 1911. Rutherford tested Thomson's hypothesis by devising his "gold foil" experiment. Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. If he shot high velocity alpha particles at an atom then there would be very little to deflect. He decided to test this with a thin film of gold atoms. Most alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly backwards. -
Neil Bohr
1913
Bohr’s greatest contribution to modern science was the creation of the bohr model.The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons. He was the first to figure out that electrons travel in different orbits around the nucleus of the atom and that the number of electrons in the outer orbit determines the properties of an element. -
Erwin Schrodinger
said that electrons didn't really moved around the nucleus in a circle, they were more like hyperactive flies moving all over the place creating a path he called this orbital. he also introduced the quantum mechanical model. this does not define the exact path of an electron, but rather, predicts the odds of the location of the electron. so this introduces sub- energy levels -
Werner Heisenburg
The theory (Bohrs) provided a good description of the spectrum created by the hydrogen atom, but needed to be developed to suit more complicated atoms and molecules. He created matrix mechanics.Werner's contribution to the atomic theory was that he calculated the behavior of electrons, and subatomic particles that also make up an atom. He said this means that electrons do NOT travel in neat orbits &all electrons that contain protons will then change momentum and physics. -
James Chadwick
bombarded beryllium atoms with alpha particles. An unknown radiation was produced. he saw this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton. This particle became known as the neutron. Neutrons are located in the center of an atom, in the nucleus along with the protons. They have neither a positive nor negative charge, but contribute the atomic weight with the same effect as a proton.
