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442 BCE
Democritus
Democritus argued that everything can be imagined to be made up of tiny pieces of pure substances. He called the tiny pieces atoms. Democritus's model stated that matter consisted of invisible particles called atoms and voids. -
322 BCE
Aristotle
Aristotle argued that everything was instead made up of four elements: air, earth, fire, and water. He also formalized the gathering of scientific knowledge. -
1267
Roger Bacon
Though gunpowder was first discovered in China, Roger Bacon was the first in Europe to record its formula and reproduce it. -
Francis Bacon
Francis Bacon formulated the scientific method, with which the laws of science are discovered by gathering and going through data from experiments and observations, rather than using logic based arguments. -
Robert Boyle
Robert Boyle wrote The Skeptical Chemist. He believed that there was more than four elements. He discovered that the volume of gas decreases with increasing pressure. -
Lavoisier
Antoine Lavoisier was known as the father of chemistry he performed systemic experiments as well as recorded the observations carefully taking note, comparing his results with others. Through experiment Lavoisier was able to come to a conclusion that the atmosphere is made of several gasses. -
Alessandro Volta
Alessandro Volta developed the first electrical battery. He discovered that electricity could be generated chemically. -
Joseph Proust
The French Chemist Joseph Proust proposed the law of definite composition or proportions based on his past experiments. -
John Dalton
John Dalton was an English school teacher who had developed an atomic theory.
One of the main theory's Dalton had was that....
All matter is made of extremely small atoms, which cannot be subdivided, created or destroyed. -
Justus Von Liebig
Justus Von Liebig used combustion to discover various elements. -
Dmitri Mendeleev
Mendeleev considered all the information on the elements that had been discovered and found periodic trends when he had arranged them by the relative mass. -
Eugen Goldstein
Eugen Goldstein worked with a crooks tube coming up with the conclusion that atoms have positively charged and negatively charge potential. -
J.J. Thomson
J.J. Thomson worked with a cathode ray tube. Thomsan observed that the charge being emitted in the cathode ray was negative. Every element that had been tested had the same result. -
Pierre and Marie Curie
The Curies concluded that uranium ore contained other radioactive elements. This led to the discovery of the elements polonium and radium. -
Heri Bacquerel
Heri Bacquerel discovered radioactivity in 1896.
After discovering uranium salts and how uranium salts are affected by light. Further studies made it clear that the was something new not x ray radiation causing the discovery of a new phenomenon, radioactivity. -
Robert Millikan
Robert Millikan calculated the electrical charge in an electron. -
Ernest Rutherford
Ernest Rutherford won a Noble Prize for studying radiation. Ernest Rutherford performed his famous "gold foil" experiment with Hans Geiger and Ernest Marsden. -
Henry Moseley
Henry Moseley published a paper with which he concluded that atomic number is the number of positive charges in the atomic nucleus. -
James Chadwick
Chadwick bombarded Beryllium atoms with alpha radiation. He had evidence of a new kind of subatomic particle, known as the neutrons.