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442 BCE
Democritus
Democritus is from Greece. He created the first atomic model which was just a sphere and nothing else. This helped other scientists understand the idea of an atom and encouraged other scientist to research more on the atom and make a generic makeup. Evidence of his experiments is that he cut a rock in half and knew that each half had the same properties as the original rock. -
422 BCE
Democritus cont.
He stated that matter consists of invisible particles called atoms and a void. He stated they were indestructible, unchangeable, and homogeneous. Said that all atoms differ in size, shape, mass, position, and arrangement, and that a void exists between them. -
322 BCE
Aristotle
Aristotle is a philosopher in Greece. Aristotle did not believe in the atomic theory. He believed that all materials on Earth were not made of atoms but made of the four elements, Earth, Fire, Water, and Air. People believed him because of Democritus’ idea that atoms are made of the four elements causing the atomic theory to be overlooked for 2,000 years. -
322 BCE
Aristotle cont.
Later scientist prove that Aristotle was wrong but his thinking was still important because it was a theory of how living things were made. -
776
Abu Musa Jabir ibn Hayyan
Jabir is from Iran. Jabir emphasizes how knowledge is gained through experience and experiments. Also showed how there are different materials other than minerals such as plants and animal substances. He also shows the importance of finding the actual densities of substances. Showed the introduced qualities of warm, cold and dry. And believed that stars influence human behavior. -
1223
Albertus Magnus
Albertus Magnus is from Germany. He established the study of nature as a legitimate science within the Christian tradition. He also experimented a lot, Experiment for Albertus indicates a careful process of observing, describing, and classifying. Became famous for his comprehensive knowledge and for demonstrating that the study of science was compatible with religious faith. -
1440
The Printing Press
During the Renaissance, was invented by Johannes Gutenberg. It revolutionized the way documents were made. -
Robert Boyle
Boyle is from Ireland. Boyle’s law is one of the most famous. It states that if the volume of a gas is decreased, the pressure increases proportionally. But his law was only able explained if all gases were made of tiny particles, so he tried to make a universal ‘corpuscular theory’. He then defined the modern idea of an ‘element’ as well as acids and bases. Which led many others to standard chemical tests -
Vacuum tube and electric generator
Vacuum tube was invented in 1650 by Otto von Guericke. It removes gas molecules from a sealed volume. He used to study combustion and respiration. -
Electric Generator
It was invented in 1663 by Otto von Guericke. They were known as friction machines, used a sulfur globe that could be rubbed and rotated. -
Henry Cavendish
Cavendish is from France. Developed a general theory of heat. His theory contained the principle of the conservation of hear and even contained the concept of the mechanical equivalent of heat. He produced “inflammable air” by dissolving metal in acids and “fixed air” by dissolving alkali in acids. He measured their solubility and their gravity and combustibility. This was later important to a Frenchman named Antoine-Laurent Lavoisier. -
Antoine-Laurent Lavoisier
Lavoisier is from France. He established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions with what he named “oxygen,” and helped systematize chemical nomenclature, among many other accomplishments -
Precision Balance
Antoine Lavoisier developed a balance that could measure mass to the nearest .0005g. -
John Dalton
Dalton is from the United Kingdom. He introduced his belief that atoms of different elements could be universally distinguished based on their varying atomic weights. His evidence are that he studied the nature and chemical makeup of air and learned that it was not a chemical solvent. He discovered Dalton’s Law of Partial Pressures: Total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space. -
Amedeo Avogadro
Avogadro is from Italy. Dalton’s Law of Partial Pressures: Total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space. -
JJ Thomson cont.
His evidence is by applying an improved vacuum technique, Thomson was able to put forward a convincing argument that these rays were composed of particles. And he concluded that all matter whatever its source, contains particles of the same kind that are much less massive than the atoms of which they form a part. -
JJ Thomson
Thomson is from the United Kingdom. He discovered the electron by experimenting with a cathode ray. He demonstrated that the cathode rays were negatively charged. He also studied positively charged particles in neon gas. He proposed a model of the atom which he likened to plum pudding because he saw that the accepted model of an atom did not account for negatively or positively charged particles. -
Mendeleev
Mendeleev is from Russia. He developed the periodic classification of the elements. He found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern periodicity, or properties within groups of elements -
William Ramsay
Ramsay is from England. He discovered 4 new gases: neon, argon, krypton, and xenon. Theses along with helium and radon were then used to form a new family of elements called the noble gases. -
Marie and Pierre Curie
They are both from Poland. Curie found out about radiation and how they depended on the element present in the compound. She then says that radioactivity doesn’t depend on how atoms are arranged but rather that it originates within the atoms. They later announced the discovery of two new elements, radium and polonium. -
Ernest Rutherford
Rutherford is from New Zealand. Discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles in helium nuclei. His experiment was that he fried alpha particles at foil. He discovered that nearly the total mass of an atom is concentrated in a nucleus. -
Niels Bohr
Bohr is from Denmark. Niels Bohr also made an atomic model and was able to account for an ever increasing number of experimental data. His evidence he conducted postdoctoral research in England with Rutherford at the University of Manchester. He proposed that electrons could only occupy particular orbits determined by the quantum of action and that electromagnetic radiation from an atom occurs only when an electron jumped to a lower-energy orbit. -
Erwin Schrodinger
Schrodinger is from Austria. He contributed to the wave theory of matter and to other fundamentals of quantum mechanics. His experiment was that he applied his equation to the hydrogen atom, and was able to accurately predict many properties. The Schrodinger equation describes the form of the probability waves (or wave function) that govern the motion of small particles, and it specifies how these waves are altered by external influences -
Werner Heisenberg
Heisenberg is from Germany. In quantum mechanics, the uncertainty principle, also known as Heisenberg’s uncertainty principle or Heisenberg’s indeterminacy principle, is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle, known as complementary variables, such as position x and momentum p, can be known. -
Louis de Broglie
de Broglie is from France. He developed a revolutionary theory of electron waves. A wave confined within boundaries imposed by the nuclear charge would be restricted in shape and, thus, in motion, because any wave shape that did not fit within the atomic boundaries would interfere with itself and be canceled out. -
James Chadwick
Chadwick is from the United Kingdom. Chadwick discovered the Neutron in atoms. They are found in the center of an atom, in the nucleus along with protons. They have no charge, but contribute the atomic weight with the same effect as a proton. -
Irene Joliot-Curie
Irene is from France. Irene’s discoveries revealed the possibility of using artificially produced radioactive isotopes to follow chemical changes and physiological processes, and such applications were soon successful; the absorption of radio iodine by the thyroid gland was detected, and the course of radio phosphorus (in the form of phosphates) was traced in the metabolism of the organism. -
Irene Joliot-Curie cont.
The production of these unstable atomic nuclei afforded further means for the observation of changes in the atom as theses nuclei broke down -
Lise Meitner
Meitner is from Germany. She discovered that nuclear fission can produce enormous amount of energy. Although she claims herself as the atom bomb she disapproves it. She believed that nuclear energy should be used solely for peaceful purposes. She wasn’t awarded with nobel prize but she was honored by getting a chemical element 109 named after her, Meitnerium. -
Rosalind Franklin
Franklin is from the United Kingdom. Rosalind took pictures of diffraction images of DNA which later led to the discovery of DNA double helix. It was confirmed with Watson that DNA had a helical structure. Her accurate interpretation of the data provided valuable insights into the DNA structure. -
Linus Pauling
Pauling is from America. He was founder of quantum chemistry, molecular biology and molecular genetics. He had several scientific concepts including valence bond theory and electronegativity. He Also discovered the alpha-helix structure of proteins and discovered that sickle-cell anemia is a molecular disease.
