-
Antoine Lavoisier's Atomic Theory
The famous chemist from France; mostly known for very carefully weighing all chemical experiements. 2 factors he founded: 1) the simplest substances, which Lavoisier called elements, could not be broken down any further and, 2) these elements always reacted with each other in same proptions. He always founded out about compounds from combining oxygen and hydrogen, which makes water. -
Dalton and His Atomic Theory
Dalton got most of his work based of the careful measurements of Antoine Lavoisier. Dalton realized that if elements were made up of atoms. And a combination of atoms are called a molecule. Dalton also came to the theory that atoms are indestructible and can not be cut anymore. From this point on, atomic theory is based off his findings. -
Henri Becquerel's Atomic Theory
Henri Becquerel was born into a science family. Becquerel did close work with potassium uranyl sulfate, which he exposed to sunlight and placed on photographic plates wrapped in black paper. When it was developed, the plates revealed an image of uranium crystals. Later experiments; Becquerel put the crystals in the light of the sun and the images were clear and strong which meant that the crystals were radioactive, so Becquerel was the first scientist to discover readioactivity. -
Marie & Pierre Curies' Discovery
The Curies are credited with discovering radium and polonium when they started to investigate radioactive substances. She found these two and many more elements from the element, uranium and it contained some traces of radioactivity. In 1903 she won the Noble Prize for physics along with Henri Becquerel. -
J.J. Thomson Makes His Atomic Discovery
J.J. Thomson discovered that all atoms have electrons outside the nucleus. He discovered this by doing a series of experiements desgined to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson electrically charged plates and magnets as evidence of "bodies smaller than regular atoms." This experiment helped him discover electrons and how they are in every single atom. -
Max Planck's Atomic Theory
Max Planck developed the quantum theory which was based off of the fact that he believed that all elements eventually lost their heat or energy over time. So he came up with the equation to figure out the energy of the atom or elements; h=6.63*10E-34 Js. His contribution helped understand atomic and subatomic processes. -
Robert Millikan's Discovery
Millkan's earliest success was the accurate determination of the charge carried by an electron, using the famous "falling-drop method." So his work was based off of what J.J. Thomson discovered about electrons in 1898. -
Ernest Rutherford's Atomic Discovery
Rutherford published his atomic theory discribing the atom as having a central nucleus (positive) surrounded by negative orbiting electrons. He found this out by doing an experiment with his gold foil model which contained a detecting screen (acting as the membrane), particle emitter, and silt. This model suggested that most of the mass in an atom was contained in a small nucleus. -
Henry Mosely
Mosely is credited with being the first man to arrange the Periodic Table in order based on element's atomic number. Mosely based his work off of Rutherford and Bohr who also were on the list. Also Mosely had studied hard with X-rays before doing the Periodic Table, so after he was done with the Periodic Table he published his results of measurements of wavelengths from X-rays. -
Niels Bohr's Atomic Theory and Model
The Bohr Model Bohr applied the quantum theory to Rutherford's atomic structure by assuming that all electrons travel in stationary orbits defined by their momentum. This led to possible energy levels for their orbits. Bohr also developed his very own model of what an atom would look like with the nucleus and the electron lines. It is called the Bohr Model as you may know. -
Werner Heisenberg's Theory
Heisenberg is best known for his theory of quantum mechanics when he was only 23 years old. His theory is based off of what we can only see, which would be the radiation emitted by the atom. Most of his work was associated with Niels Bohr. SO he was big on the electron deal; he stated that "We cannot always assign to an electron a position in space at a given time, nor follow it in its orbit." -
Erwin Schrodinger
Schrodinger laid the foundation of the wave-mechanics approach to the quantum theory, which was based of Max Planck. He also put his now-famous equation out for the world to see. His theory was based off of energy levels in the atom. -
Chadwick's Neutral Discovery
James Chadwick discovered the neutrally-charged neutron. After a decade long struggle, Chadwick did a test on Beryllium and bombarded the element with alpha particles. This caused some of the protons to be discharged, creating neutrons. -
Democritus discovers first atom
Democritus discovers his atomic theory about atoms around 400 B.C.E. His theory states that everything around us is made up of atoms. He also stated that atoms are indivisble and cannot be broken down. Finally, he said that in between the atoms, there is a bunch of free space and the morfe empty space there is, the heavier the atom gets. Democritus help influential help from Leucippus, his mentor. (Couild go to B.C.E and the earliest date i could get was 100 A.D.) -
Democritus
Democritus also came to the conclusion that if you keep cutting an object until it can't be cut anymore would be called an a-tom meaning in Greek no-cut. -
Aristotle's Atom and His Disagreement with Democritus Theory
Aristotle's atomic theory was based off water, fire, earth, and air; he also believed there were 4 qualities to these elements; hotness, dyness, coldness, and moistness. He thought of this because he didnt believe in atoms because they were "ultimate small." There were two forces: conflict and harmony, conflict was for the bad things and harmony was for the good. Aristotle also believed in a fifth element comprised of the heavens, which was the ruler of all the elements. -
Period: to
History of Atom Timeline
