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Democritus
The Greek philosopher Democritus of Abdera developed the idea that everything is made of atoms. Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until they stopped. In Democritus philosophy, atoms existed not only for matter but also for such qualities as perception and the human soul. -
Dalton
Democritus first suggested the existence of the atom but it took almost 2000 years before the atom was placed of a solid foothold as a fundamental chemical object by John Dalton. He believed that the atom was a solid, indivisible sphere, with different types of atoms for different elements. John Dalton developed a theory that matter is simply composed of atoms of different weights and is combined in ratios by weight. -
J.J. Thomson
Joseph John Thomson discovered electrons but believed they were mixed with positive charges (later named protons) throughout the atom in a “plum-pudding” matter. The plum-pudding model was proposed in 1904 before the discovery of the atomic nucleus in order to add the electron to the atomic model. -
Max Planck
Max Planck was a German scientist that created the Quantum Theory. In this theory, Planck stated that energy was given off in little packets of energy. These were called photons when talking about light. He discovered that the energy in wave form is restricted to specific quantaties. This discovery led to the understanding of energy levels in atoms, since quantums are leaps in the atom. This discovery later added to the advance in the atomic model. -
Hantaro Nagaoka
Nagaoka developed an early, incorrect "planetary model" of the atom. -
Robert Millikan
Robert Millikan was an American scientist that was very interested in J.J. Thomson's finding of the electron. J.J. Thomson predicted that the electron was 1000 time smaller than the atom. Millikan wanted to prove this hypothesis. He preformed an "oil-drop experiment" in which he found that J.J. Thomson was correct. Millikan was also involved in the Quantum Theory after he was inspired by Max Planck. Millikan inspired other scientists to explore parts of the atom. -
Ernest Rutherford
Ernest Rutherford was another scientist that changed the atomic model. He felt that J.J. Thomson's model was incorrect, so he created a new one. He created the nucleus, and said that instead of the positive matter being the whole atom, it was just in the middle. He said the atom was mostly empty space and that the electrons surrounded the positive nucleus. This model influenced one of his own students to perfect the atomic model later on. -
Neils Bohr
Bohr believed that the electrons were located outside the nucleus traveling in paths called energy levels. Bohr's theory became the basis for quantum mechanics,which explained in greater detail the complex structure and behavior for atoms. -
Louis de Broglie
He developed a theisis of important findings. How: It served as the basis for developing the general theory now known by the name of wave mechanics, a theory which has utterly transformed our knowledge of physical phenomena on the atomic scale. -
Erwin Schrodinger
Erwin Schrodinger hypothesized the Electron Cloud Model in which the electrons are found in probable locations outside the nucleus in energy levels and that the atom is mostly empty space. -
The Great Depression
On October 24, 1929, a stock market crash occurred in the United States. This event was the beginning of the Great Depression, which lasted for ten years. -
James Chadwick
Chadwick proved the existence of neutrons. Chadwick discovered neutrons which exist with the protons in the nucleus. He won the Nobel Prize in 1935 for his discovery. -
Assassination of John F. Kennedy
John Fitzgerald Kennedy was assassinated on November 22, 1963 in Dealey Plaza, Dallas, Texas. He was seriously shot while traveling with his wife and the latter’s wife in a Presidential motorcade. It was investigated that he was assassinated by Lee Harvey Oswald. The assassination was suspected that it was due to conspiracy. This event really shocked everyone, thus is actually one of the most important events in U.S. history. -
The Beatles on the Ed Sullivan show
The Beatles performance on Ed Sullivan was unforgettable. They opened with “All My Loving” to the screeches from teen-aged girls in the audience. The Beatles then followed that hit with Paul McCartney singing “Till There Was You,” before wrapping up the first set with “She Loves You.” The hour-long Ed Sullivan Show broadcast concluded with The Beatles singing two more of their hits, “I Saw Her Standing There” and “I Want to Hold Your Hand.” -
Apollo 11
U.S. space mission that landed Neil Armstrong on the moon. -
The Challenger
Space shuttle Challenger launched on January 28, 1986. Christa McAuliffe, a teacher, was aboard the spacecraft. Challenger exploded just 73 seconds after takeoff, an accident that occurred due to several factors.
