History of the Atom

1803

John Dalton

The year of discovery was 1803 and he discovered that all things contained particles called atoms. His model was called the billiard ball model. The billard ball model, which is what he used to describe what atoms looked like and that elements consisted of little particles, he had envisioned them to look like billard balls so he made wooden balls to model them. He said atoms of a given element are identical in size, mass, and other properties. He had investigated pressure and propterties of gas, so he could see the thhat the gas consisted of the tiny particles. His discovery was important because it was the first complete attempt to all matter in the atom and properties.

1834

Dmitri Mendelev

The year of discovery was 1834. The name of the key discovery was the Periodic table. The periodic table is a table with all the chemical elements in order with their atomic weight. He had been studying alkaline earths, eh had realized that the atomi weight order could also be used to arrage elements within each group but also within themselves. His findings were important because he was able to find charachteristic of elements that were undiscovered, and this is something scientist still use today.

1896

J.J. Thomsen

The year of discovery was 1896. The name of the model was the plum pudding model or Thomson Atomic model. The plum pudding model was to describe how the parts of the atoms were, and it was seen as the postive medium was seen as pudding, with plums (electrons) inside. The experiment that led to this finding was cathode ray tubes that showed that all atoms had negative charged particles/electrons. This finding was important because it would effect the way scientists thought about atoms and ramifications for physics,

Robert Milikan

It was the year 1909 of Robert Milikan's discovery. The name of the key discovery was discovering electron charge and mass. He had discovered the value of electron charge. He had been doing an oil drop experiment where he was able to measure electic force and electric field on the tiny charge of an oil droplet. His finding was important to the development because he helped future scientist with this information.

1909

Ernest Rutherford

The year of discovery was 1909. The name of the model was the planetary model. He had been able to describe the atom as tiny, dense, and postive charge, which is the nucleus, and that the postive charge is not like pudding. The experiment that he did was called gold foil experiment where he had a beam of particles passed through the foil, but some foil got scattered which showed that the atom has empty space surronding a nucleus. This was an important finding because it showed that J.J. Thomson's discovery was wrong, and he discovered atomic nucleus.

De Broglie and Schrodinger

In 1924 they developed a probabilistic model of the atom. This model was also known as the wave mechanical model. This model allowed electrons to act like particles and waves and be able to obtain orbitles. Orbitles are the areas of probability even though it sounds like the word orbits it has nothing to do with it. In order to come up with their model they conducted an expirement called "Schrödinger's cat". The way this experiment worked ina cat was placed into a box with a vial of posion where if the vial was to break its because some atom died. Which the atoms are then observed. This discovery helped with the development of atoms since it caused atoms to be treated mathematically as matter waves.

James Chadwick

In 1932 he proved his dicovering of nuetrons. Nuetrons are a particle that lacks a electrical charge so basically has no electrical charge. He confirmed the existense of them by an expirement where he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. His discovery caused the development and chaning the model of an atom since it added a new particle to it. In the new model it now included the new nuetron particle inside in the nuclues with the protons. As you can see in the model, the electrons and protons have a label of their electrical charge and since neutrons have a neutral charge it doesn't need a label.