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Democritus
Democritus was born in c. 460 BC and died in c. 370 BC. During this time he started the whole atomic theory. His array of knowledge and the importance of his influences on both the Greeks and the modern evidence he was discovering he was just like the Aristotle of the 5th century. Democritus was the person who came up with a name for the atom. This is how an atom became an atom. -
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Democritus
Democritus’ atomic theory was that there was a simple round sphere; he hadn’t discovered electrons, protons or neutrons. All he discovered was that it was a round sphere. He was the creator of the very first atomic model. He helped many people with understanding the discovery of the atom and he helped other scientists look further into what the general makeup of the atom is. -
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Democritus
The atomic theory was declared that “The universe is composed of two elements: the atoms and the void in which they exist and move.” As stated by Democritus the atoms were minute amounts of matter. Democritus’ other theory was that the atom could not be destroyed, atoms are always moving, atoms are solid but invisible, atoms are all identical and atoms differ in size, shape, mass, position, arrangement and temperature. He also assumed that there were an infinite number of atoms in the world. -
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Democritus
Another theory Democritus had was that solids were made up of small, pointy atoms, liquids were made up of large, round atoms and oils were made up of very fine, small atoms that can easily slip past one another. -
Isaac Newton
Isaac Newton was born in 1642 and died in 1727. During this period of time Isaac Newton contributed to the atomic theory. Isaac tried many discoveries that were very similar to Johannes Kepler and the laws Johannes made. Isaac created classic mechanics, which was the beginning of the modern physics. He made many achievements but one of his greatest is discovering the laws of gravity and movement. -
Isaac Newton
Newton formulated the laws of the universal gravitation; he said that it demonstrated the motion of the objects on earth. He worked from Kepler’s laws and removed the last doubts of the heliocentric model. -
Antoine Lavoisier
He also discovered that a chemical compound could not be created or it could not be destroyed. Lavoisier proved that diamonds and graphite are both different forms of carbon and by burning each of them it makes a carbon on dioxide. He also proved that a candle burning and humans exhaling both create carbon dioxide. Lavoisier created a book that named an overall amount of 33 elements and most of these we still use today and his wife did the sketches and made the book. -
Antoine Lavisier
Some of the elements or substances that were discovered and put into this book included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. Lavoisier had a theory that the idea of an element as a substance, which was unable to be broken down by any known method of chemical analysis was clarified and Lavoisier theory was the beginning of the chemical compounds from an element. Lavoisier was able to make an accurate measurement of the structure of the chemical compounds. -
Antoine Lavoisier
Antoine Lavoisier was born in 1743 and died in 1794. During this time Lavoisier contributed to the atomic theory and most of his theories are still true to this day. Lavoisier was called the ‘Father of Modern Chemistry’ because he was the person to discover that hydrogen is made up of water and oxygen. Lavoisier also that when the oxygen and hydrogen mixed together they sometimes produced a dew which was an inflammable substance but still turned out to be water. -
Antoine Lavoisier
Lavoisier also proved that air was a mixture of gases, which mostly consisted of nitrogen and oxygen. He discovered that the oxygen played a big part in the rusting of metal and the respiration of animals and plants. The experiment that Lavoisier undertook proved that respiration was a slow intake of natural materials, by inhaling oxygen. This helped scientists understand the growth and survival of animals and plants. -
John Dalton
John Dalton was born in 1766 and died in 1843. During this time he did a great amount of work towards the atomic theory. Dalton had the theory that matter could not be broken down any smaller. He came up with the term atom to describe the tiny particles. It took a while before his ideas where recognised as an important theory it is now. -
John Dalton
A lot of Dalton’s important contribution to the atomic theory was his theory that matter is made up of atoms of different weights and combines simple ratios by weight. This theory gave scientists ways to explain evidence about atoms. 30 years before Dalton’s theory Antoine Lavoisier made accurate measurements of the structure of chemical compounds. -
John Dalton
Using this information Dalton discovered that the chemical compounds contain more than one element and are formed by one element combines with atom of other elements with the set amount. All atoms of an element are exactly the same. Elements are made up of atoms. The compound we now call carbon dioxide used to be called ‘fixed air’ because air was much lighter then it and other substance weren’t allowed to burn in it. -
John Dalton
They discovered that oxygen in fixed air always had a mass 2.66 times the mass of carbon in the compound. This example is now called the ‘law of constant composition.’ Dalton also discovered that you can’t create or destroy an atom in a chemical reaction. Scientists have used Dalton’s atomic theory to make testable predictions supported by a range of evidence. -
John Thomson
With this evidence and knowing that the opposite charges attract each other to move together, he came up with the plum pudding. Thomson said that the positive charged material is the cake and the electrons are the fruit. This was called the ‘Thomson plum pudding model’ of the atom. It was also know as the chocolate chip cookie or the blueberry muffin. The theory was tested and it was proven to be wrong, the atom is mostly filled with empty space. -
John Thomson
Joseph John Thomson was born in 1856 and died in 1940. During this time he contributed a lot towards the discovering more about atoms. Thomson discovered that atoms were divisible and that they are made up of even smaller particles. The experiments showed that the insides of the atoms have negatively charged particles, which are now called electrons. Thomson also showed that atoms have positively charged material, but he wasn’t sure what material this was. -
John Thomson
Although Thomson’s theory was wrong it influenced other scientists to research it and find out more accurate results, which resulted in a more accurate model/theory. He also discovered that most atoms were neutral. Thomson discovered that the hydrogen has only one single electron per atom, in previous theories they thought it had numerous electrons. -
Max Planck
Max Planck was born in 1858 and died in 1947. During this time he contributed a lot towards the atomic theory. Max Planck described that the energy is not an on going and is like a motion of an object, but it is carried in a tiny, broken units which he called quanta and explained it as “the pennies of the atomic theory.” Planck defined that the each of the quantum’s energy is equal to the amount of radiation times by the general continuous energy. -
Max Planck
Plank’s work was acknowledged more, after Albert Einstein determined that the photoelectric effect and Neils Bohr applied a simple principle to the atom that was a replaces Ernest Rutherford’s atomic model. Max Planck also worked on research of chemical bonding, a kinetic theory, molecular revolving range, a white light and the properties of the metals. Planck was very faithful to the German government during the Nazi era. -
Max Planck
Planck became an allied of Berlin during World War II because they demolished his home in Berlin, also along with most of the paper documents of his all work. Max Planck contributed to the construction of the bombs used in the war. The only experiment that Max Planck did in his scientific career was spreading hydrogen through a heated piece of platinum. -
Hantaro Nagaoka
Hantaro Nagaoka started to develop the planetary model of an atom in 1904 and the model was based around a parallel to the description of the Saturn rings, which is that the rings are stable because they orbit around a very massive planet. -
Hantaro Nagaoka
Hantaro Nagaoka was born in 1865 and died in 1950. During his time he contributed towards the atomic theory. Hantaro Nagaoka began to work on the structure of an atom, but because of the discovery by J.J. Thomson of the negatively charged electron hinted that the neutral atom must also have the opposite of positive charge. -
Hantaro Nagaoka
Hantaro Nagaoka’s model is made up of two of the predictions which were a nucleus is very massive which is the planetary model and the electrons were moving around the nucleus and is bound together by electrostatic forces, which is like the rings moving around in a circle around Saturn bound by the gravitational forces. Both of Hantaro Nagaoka’s predictions were both confirmed by Rutherford. -
Hantaro Nagaoka
But parts of Hantaro Nagaoka’s predictions were proved wrong because the charged rings would be unstable if it was uneven, which is not the case for the Saturn’s rings. This is when Hantaro Nagaoka abandoned the theory in 1908. -
Robert Millikan
Robert Millikan was best known for his work in the atomic physics and important science. He dealt with the basic components of the universe, the forces they apply to one another and the outcome formed by these forces. -
Robert Millikan
Robert Millikan was born in 1868 and died in 1953. During this time he contributed towards the atomic theory. To measure the charge of the electron in an atom as well as the electron mass and the Avogadro's number since this was unknown Millikan and one of his graduate students Harvey Fletcher used the oil-drop experiment. This experiment was carry out by spraying tiny oil droplets and then had them fall through a small, charged hole into a closed area. -
Robert Millikan
Then the oil droplets had a charge on them. Millikan then inserted the closed area into an electric field. Then the charged oil particles could now move up and down when he urged them to. By looking at how fast the particles were moving he was able to find out what the charge of just one single electron: 1.6*10-19 Coulombs. This is how he could determine the charge on the electrons. But it was J.J. Thomson who discovered that the electrons actually exist in the first place. -
Ernest Rutherford
Ernest Rutherford was born in 1871 and died in 1937. In this time he contributed a large amount towards the atomic theory. Rutherford was one of Thomson’s former students and he proved that the plum pudding theory was wrong. He the results ended up showing that the atom is mostly filled with empty space. This changed the way people and scientists thought about the inside of the atom. -
Ernest Rutherford
The alpha particles went through the gold foil with no deflection and the alpha particles that travelled with high amounts of energy bounced right back the way they came. This evidence showed that the gold atom contains a lot of space, but some areas of the atom contain fairly large amount of positive charge. -
Ernest Rutherford
They carried out the experiment by setting up a very thin layer of gold and fired of steam alpha particle at it. The alpha particles contain 2 protons, 2 neutrons and had a positive electric charge. Detectors, set up around the gold foil, recorded the alpha particles to see if the alpha particles had gone through the foil or if it had been deflected. -
Ernest Rutherford
This is how Rutherford proved that the plum pudding theory was not accurate, because a fairly big area of space containing negative charged electrons surrounded the positive ‘nucleus’ of the atom. This changed the way scientists looked at the structure of the atom. -
Ernest Rutherford
Overall Rutherford discovered that the nucleus is made up of protons and neutrons, protons carry positive electric charge, neutrons are neutral they have no electric charge and neither does an electron, electron moved around in the space outside the nucleus and an atom is mostly empty space. -
Albert Einstein
Einstein played a part in the statistical engineering by his establishment of the quantum theory of a monatomic gas. Einstein also achieved some useful work with the connection of the atomic transition probabilities. Einstein gave an explanation of the similarity of mass and energy which was revealed in a famous equation e=mc2. He also proved the existence of the atom in 1905 using a microscope. -
Albert Einstein
Einstein was capable of accurately calculating the standard distance submerged visible particle would move in a given amount of time. The not visible particles were able, to be tested and measured by looking at the movement of the visible particles, using a microscope and a stopwatch. With these calculations you could decide on the size of the not visible atoms and molecules. Also Einstein’s theory that heat is a solution of the motion of the atoms and molecules was proved to be right. -
Albert Einstein
Albert Einstein was born in 1879 and died in 1995. During this period of time Einstein contributed a lot towards the atomic theory and he invented a couple of new things too. Einstein first became famous for his theory of relativity, which lead up to the basis of the revealing of the atomic energy. Einstein looked into the thermal properties of light and with the low radiation solidarity, his examination laid down the base of the photon theory of light. -
Hans Geiger
Since they discovered that the alpha particles can penetrate off thin walls of solids Rutherford and Geiger thought that they would just go right through atoms because most of the atom is empty space. To carry out this experiment Geiger invented a machine that would shoot alpha particles though the gold foil onto a screen, where there they observed the flashes of lights. -
Hans Geiger
Counting all the flashes of light was also a hard job too so Geiger inverted another machine that would count all the flashes per minute. His resolution for this was the early version of the “Geiger counter,” which was an electrical machine that was aimed to count each release of alpha particles. This counter could locate a speeding alpha particle within about a one-centimetre gap and within a hundred-millionth second of time. -
Hans Geiger
This enhanced the gold foil experiment because the machine helped to make this experiment easier and quicker to complete. Geiger used his machine to confirm the existence of he light quantum or packets of energy. -
Hans Geiger
Hans Geiger actual name is Johannes but they call him Hans for short, he was born in 1882 and died in 1945. During this period of time he contributed a lot towards the atomic theory and many of the experiments used. Geiger and Rutherford began experiments based around the discovery of the alpha particles, which are “positive” electric charges from the radioactive substances, which is when an atom gives off a particle of matter and also harmful rays of energy. -
Neils Bohr
Neils Bohr was born in 1885 and he died in 1962. Neils Bohr contributed a lot towards the atomic theory. Bohr researched the structure of an atom, after the recent discovery by Rutherford of the atomic nucleus. Bohr used the Quantum Theory discovered by Planck, to work out and show a picture of the atomic structure with the latest improvements. Bohr’s model in based around quantum mechanics. -
Neils Bohr
Although the Bohr model did have some errors, it was still very important because in explained most of the recognized characteristics of the atomic theory, without having the entire high-level maths of the modern version. Bohr model is planetary model and is when the negative charged electrons, orbit around a small positive charged nucleus, like the plants orbiting around the sun. -
Neils Bohr
Between the positive charged nucleus and the negative charged electrons the electrical force is similar to the gravitational force of the solar system. The electrons orbit the nucleus and the orbits have a set size and energy. He size of the orbit is related to the size of the orbit energy. The hydrogen atom (Z = 1) or for a hydrogen-like ion (Z > 1) is the most straightforward example of the Bohr model. -
Neils Bohr
An electric magnetic field will be either absorbed or released if an electron moves from one orbit to another orbit. The principle quantum number is n and the radius of practical orbit increases by n2. -
Erwin Schroedinger
Erwin Schrödinger was born in 1887 and died in 1961. He contributed a lot towards the atomic theory during this period of time. Erwin Schrödinger was an Australian physicist and he established a number of core results in the field of the quantum theory. This developed a wave of mechanics, which formed the wave equation, a stationary time-developed Schrödinger equation and showed the identity of his development of the formalism and matrix mechanics. -
Erwin Schroedinger
Erwin Schrodinger said that rather than the electrons being spread out among an electron layout of the shells and energy levels, they are arranged to orbit around the nucleus and organized within the Electron Clouds. He described an orbital as an area of space the surrounds a nucleus in which the two electrons can move randomly around the nucleus. This stands for the Quantum Model of Electrons and explained more about the chemical phenomena and the simple Particle or Corpuscular Model. -
Erwin Schroedinger
Erwin Schrödinger’s wavelength experiments displayed that all matter always acts as waves, which also meant that the electrons in the atom were much more wavelike too. Erwin Schrödinger discovered that the movement of an electron in an atom was just like a wave. He helped other scientists understand where the electrons were in an atom and where they were moving inside the atom. -
Ernest Marsden
Ernest Marsden was born in 1889 and died in 1970. During this time Ernest Marsden helped others to work towards different atomic theories. Ernest studied under the supervision of Ernest Rutherford and Hans Geiger. Marsden achieved looking at the path of the, a -particles in Rutherford’s famous “gold foil experiment,” because Marsden was the human eye look through the telescope for days on end. Marsden was their detector for this experiment. -
Ernest Marsden
Marsden and Geiger spent most of their time working on this experiment in the “gloomy cellar” of the physics laboratories, watching for the tiny flashes that meant the unlikely spring backs of the, a -particles. About 1 in 8,000 did this and the result was published in 1909 as "On a Diffuse Reflection of the α -Particle," which formed the basis for Rutherford’s nuclear model of an atom and also the discovery of the proton. -
Ernest Marsden
In the very same year he helped Geiger on developing the Geiger counter to enhance the experiment of the gold foil to another level. Geiger and Marsden still continued on with studying the deflection of the, a -particles and the observation in 1913, after looking at over 100,000 flashes at rate of 5 to 90 per minute, they came up with the matching nuclear charge with the atomic number. -
James Chadwick
James Chadwick was born in 1891 and died in 1974. During this time his contribution towards the atomic theory was very helpful. He became an English Nobel Laureate in physics, given an award for discovering the neutron. Chadwick joined the Technical University of Berlin and there he studying under Hans Geiger and Ernest Rutherford on Research Fellowship. -
James Chadwick
Chadwick worked on converting an atom, molecule or substance into an ion of phosphorus and on the photochemical reactions of chlorine and carbon monoxide, with help from Charles D. Ellis. Chadwick’s discovery of an unknown particle in the atomic nucleus was crucial for the nuclear fission of uranium 235 to understand. Because of Chadwick’s discovery of the neutron it made it possible to make elements that were heavier than uranium inside the laboratory. -
James Chadwick
James Chadwick predicted that an atom would contain a neutron and he had evidence to prove the existence of the neutrons. Chadwick recognized the numbers of protons in an atom, which determines the atomic number. During World War II Chadwick travelled to America and there he played a part in the Manhattan Project, in the development of the world’s first atomic weapons. The atomic bombs. James Chadwick also measured the energy of the protons coming out of the hydrogen atoms.
