The History of the Atom is a vast and ever-growing discovery. From elements to cathode rays to plum pudding models to quantum physics, scientists have discovered many different ways to describe and interpret the atom.
Leucippus and Democritus
2500 years ago, in 400 B.C. a philosopher named Leucippus and his student Democritus developed the theory of the Atomism. This is the idea that matter is composed of minuscule particles they called 'Atomos' (uncuttable or indivisible). They also proposed that all changes in matter are a result of changes in the groupings of atoms. Aside from this, they made the assumption that the properties of matter are reflected in the properties of atoms in which the matter is contained.
Leucippus and Democritus
2500 years ago, in 400 B.C. a philosopher named Leucippus and his student Democritus developed the theory of the Atomism. This is the idea that matter is composed of minuscule particles they called 'Atomos' (uncuttable or indivisible). They also proposed that all changes in matter are a result of changes in the groupings of atoms. Aside from this, they made the assumption that the properties of matter are reflected in the properties of atoms in which the matter is contained.
![Picture](/uploads/4/6/6/9/46692131/732155297.jpg)
This atomic theory is the pioneer theory of Atomic Theory. For a long time after this theory was proposed, there was no new activity or discovery of the atom. However, in the late 1700s and early 1800s, scientists begin to explore the concept once more.
Antoine Lavoisier
Lavoisier was a French chemist and scientist, and is widely known to be the pioneer of modern chemistry. He was the first to find elements and put together the first periodic table of elements. In 1780, he proposed the Law of Conservation of Mass, which states that even if matter changes shape or form, its mass stays the same.
James Dalton
Dalton was an English chemist best known for 'pioneering modern atomic theory'. He defined and determined that elements exist as discrete packets of matter, and that each packet of matter has its own atoms which could not be split. He based this on Leucippus and Democritus' theory made back in 400B.C. Dalton also proposed that each element's atoms were different from one another.
Then, in the 1870s, scientists began to probe what objects were made of using devices called discharge tubes. These were gas-filled tubes with electrodes at each end which emitted light when an electrical current passed through. This had a negative charge and was produced by a negative electrode called a cathode.
Eugen Goldstein
Goldstein was a German physicist who, in 1886, discovered the proton by nothing that the positive electrode from the discharge tubes mentioned also emitted light.
Below: Diagram of Goldstein's theory.
Antoine Lavoisier
Lavoisier was a French chemist and scientist, and is widely known to be the pioneer of modern chemistry. He was the first to find elements and put together the first periodic table of elements. In 1780, he proposed the Law of Conservation of Mass, which states that even if matter changes shape or form, its mass stays the same.
James Dalton
Dalton was an English chemist best known for 'pioneering modern atomic theory'. He defined and determined that elements exist as discrete packets of matter, and that each packet of matter has its own atoms which could not be split. He based this on Leucippus and Democritus' theory made back in 400B.C. Dalton also proposed that each element's atoms were different from one another.
Then, in the 1870s, scientists began to probe what objects were made of using devices called discharge tubes. These were gas-filled tubes with electrodes at each end which emitted light when an electrical current passed through. This had a negative charge and was produced by a negative electrode called a cathode.
Eugen Goldstein
Goldstein was a German physicist who, in 1886, discovered the proton by nothing that the positive electrode from the discharge tubes mentioned also emitted light.
Below: Diagram of Goldstein's theory.
![Picture](/uploads/4/6/6/9/46692131/376510511.gif)
Joseph John Thompson
Thompson discovered the electron. J.J. Thompson measured how much heat a cathode ray generated, and how much they could be bent by magnets. He determined that the mass of the rays were 1000 times lighter than the mass of hydrogen and he renamed the 'rays' to negatively charged particles called corpuscles (known in the modern day as electrons). Overall, the atom has a neutral charge, which therefore means that there were negatively charged electrons distributed in a positively charged shell. With this theory, Thompson then went on to create the atomic model known as the 'plum pudding model'. The model was called this because of its contents, and the way it resembled a plum pudding.
Thompson discovered the electron. J.J. Thompson measured how much heat a cathode ray generated, and how much they could be bent by magnets. He determined that the mass of the rays were 1000 times lighter than the mass of hydrogen and he renamed the 'rays' to negatively charged particles called corpuscles (known in the modern day as electrons). Overall, the atom has a neutral charge, which therefore means that there were negatively charged electrons distributed in a positively charged shell. With this theory, Thompson then went on to create the atomic model known as the 'plum pudding model'. The model was called this because of its contents, and the way it resembled a plum pudding.
![Picture](/uploads/4/6/6/9/46692131/497363540.png)
Ernest Rutherfort
In 1909, scientist Ernest Rutherford designed an experiment which determined the position of particles in one area, and developed the idea of a nucleus in an atomic model - therefore changing JJ Thompson's model. He also determined that most of the atom is empty space, and found protons inside the nucleus.
In 1909, scientist Ernest Rutherford designed an experiment which determined the position of particles in one area, and developed the idea of a nucleus in an atomic model - therefore changing JJ Thompson's model. He also determined that most of the atom is empty space, and found protons inside the nucleus.
![Picture](/uploads/4/6/6/9/46692131/309250378.gif)
Niels Bohr
Bohr studied with Rutherford, and in 1911, he applied the principles of Max Planck and Albert Einstein in their explanation of electromagnetic energy (1900) and corrected Rutherford's Atomic Model. The model he developed is a model which can be seen as an example in the modern day as well.
Bohr studied with Rutherford, and in 1911, he applied the principles of Max Planck and Albert Einstein in their explanation of electromagnetic energy (1900) and corrected Rutherford's Atomic Model. The model he developed is a model which can be seen as an example in the modern day as well.
![Picture](/uploads/4/6/6/9/46692131/402065653.jpg)