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John Dalton Part 1
John Dalton was credited with first real "Atomic Theory." This theory was made after his experiments with gasses and his discovery of the Law of Partial Pressures that in a mixture of non-reacting gasses, the total gas pressure is equal to the sum of the partial pressures of the individual gasses. -
John Dalton Part 2
Dalton's Atomic Theory is:
1. )The elements are made from atoms, which are tiny particles that are to small to see;
2.) All atoms of a particular element are the same.
3.) Atoms of different elements have different properties, masses, and their chemical reactions are different.
4.) Atoms cannot be created or destroyed or split.
5.) In a chemical reaction atoms either link to one another or separate from one another. -
John Dalton Part 3
Dalton's theory is important because he was the first one in 2000 years, since Democritus, to revisit the issue of atoms which had fallen out of fashion. Dalton also created the first chart for atomic weight. His theories were quickly accepted by the scientific community. -
Dmitri Mendeleyev
Mendeleyev discovered the periodic law and created the periodic table. He systematically arranged dozens of known elements by atomic weight in a grid-like diagram. Using his table, Mendeleyev also predicted the existence and qualities of new elements. He also wrote a book called, "The Principles of Chemistry" which was very popular. Mendeleyev's reputation grew as his theories were proven true, i.e., elements whose behavior did not agree with his predictions were measured wrong. -
Marie Curie Part 1
Marie Curie is credited for finding Polonium and Radium, two new elements, and she was the first to discover how radioactivity can treat tumors. Marie Curie discovered that Polonium, was 300 times more radioactive than Uranium, and discovered that Radium was always hotter than its surroundings. She is the only person to win the Nobles Peace Prize in both physics and chemistry. -
Marie Curie Part 2
Marie Curie made several discoveries for Uranium: 1. Uranium rays charge the air as they pass through; 2. The rays coming from Uranium come from within the atom; 3. Uranium minerals Polonium and Radium are s lot more active than Uranium; 4. Thorium emits rays like Uranium. Radium's compounds are radioactive or hotter than its surroundings. Marie Curie's theory about radium's atom is that it is in a process of evolution and not stagnant. -
J.J. Thomson
Thomson discovered the electron and invented the mass spectrometer. He proved that the atom could be divided and found electrons. Thompson's erroneous "Plum Pudding" model of the atom was that the atom is a uniformly charged "pudding" and inside it "plums" or electrons orbited. This was one of the first models of the atom. In 1907, Thompson proved that every atom of hydrogen has only one electron; and in 1912, he discovered stable elements can exist as isotopes. -
Ernest Rutherford Part 1
Rutherford discovered the atomic nucleus of the atom. Its mass is a concentrated dense nucleus. Its volume was empty space, and electrons orbited the nucleus. This replaced the plum pudding idea. In 1919, Rutherford deliberately transformed nitrogen into oxygen, and in 1920, he discovered the proton and neutron, particles in atomic nuclei, that radioactive elements emit positive and negative radiation, and radiation's unique way of decreasing (half lives) until its stable. -
Ernest Rutherford Part 2
Rutherford's discoveries were important because this was a break through. Until now the model and theory was that there was nothing in the middle and that atoms had no nucleus. After this discovery more scientist wanted to know more about the nucleus and the atom. -
Niels Bohr Part 1
Bohr is credited with completely changing how er see the atom with his planetary model. He discovered that protons were in the nucleus and electrons orbited the nucleus like the planets orbiting the sun. This was a breakthrough for the science community and the founding of quantum mechanics and quantum physics. -
Niels Bohr Part 2
Bohr showed that chemical properties of the elements result from the behavior of the electrons in the highest and stablest orbit (valance electrons). This theory explained the periodic table and established quantum chemistry. In 1939, he helped produce the liquid drop model for the nucleus.
