Timeline About the Atom

  • 350


    Aristotle (350 B.C.) disagreed with Democritus' atom model because he believed that different substances made up everything on Earth. He did not have a model because he intinally believed that atoms did not exist.
  • 400


    Democritus was the first scientist to create an atom model. He was also the first to find that all things are made from tiny, invisible particles called atoms. He found that atoms are solid and indestructable, thus deriving the name atom, which means uncuttable. His model depicted just a round, solid ball because he did not know anything else about the atom at the time.
  • Jan 1, 1268

    First Eyeglasses

    First Eyeglasses
    Eyeglasses were believed to be first made in Italy from 1268-1289. The inventor is still unknown today. The earliest eyeglasses were worn by monks and scholars. They were either held in front of the eyes or they were balanced on the nose.
  • Jul 1, 1553

    Bloody Mary

    Bloody Mary
    Mary I of England was the queen of England and Ireland from July 1553 until her death in November 1558. She was most famously known as "Bloody Mary" because she killed anyone that in her way of royalty. When she killed, she killed in the most extreme measures. She had disposed of Lady Jane Grey, who was queen before her, by beheading her. She had also over 280 religious dissenters burned at teh stake in the Marian persecutions.
  • Virginia Dare

    Virginia Dare
    Virginia Dare is believed to have been the first child and first girl to have been born in America Her grandfather, the colony's governor, left for England for supplies 9 days after her birth. A few years later, when he returned, his family and the other 120 settlers of Roanoke Colony had disappeared. Virginia Dare's death date is still unknown today as well as who had abducted her, her family and the rest of the colony. Roanoke Colony is considered the "Lost Colony."
  • American Revolutionary War

    American Revolutionary War
  • Antonie

    Lavosier was the one who founded the first few elements and compiled the first table together. He used Aristotle's ideas and created different experiments investigating combustion and oxidation. By doing so, he founded some important elements, such as sulfur, oxygen, hydrogen. He also found how water was made and that air contained nitrogen. He compiled the first chemistry textbooks and tables.
  • Joseph Proust

    Joseph Proust
    Joseph Proust proposed the the Law of Constant Composition in 1799. He also stated the Law of Definite Proportions. The law states that the ratio of elements in a compound is always the same/constant. He also hinted at the 'lego'ness of matter; he believed that matter could be put together in certain patterns to make bigger, different, unique matter.
  • John Dalton

    John Dalton
    John Dalton was an English chemist that created the Atomic Theory of Matter, a composition of previous findings by Democritus and his own findings. He included in this theory that all matter is made of atoms, that atoms cannot be created nor destroyed and also, atoms of different elements combine in whole ratios to form chemical compunds.
  • Amadeo Avagadro

    Amadeo Avagadro
    Amadeo Avogadro proposed what is now known as Avogadro's Hypothesis. The hypothesis states that at the same temperature and pressure, equal volumes of gases contain the same number of molecules or atoms. When this is combined with Joseph Gay-Lussac's Law of Combining Volumes, the only possible formulas for hydrogen, oxygen and water are H2, O2 and H2O, respectively.
  • Iowa

    Iowa achieved statehood on December 28, 1846. It was first seen as land, but only in the way of thr Louisiana Purchase, which was bought by President Thomas Jefferson in 1803.
  • American Civil War

    American Civil War
    American Cival War' >American Civil War</a>
  • William Crookes

    William Crookes
    Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass.
  • Henri Bequerel

    Henri Bequerel
    Henri Becquerel was born into a family of scientists. With influences from his father and grandfather, Bequerel worked with properties of the atom, such as magnetism and radioactivity. His biggest achievements were in the field of radioactivity. In his earlier works, Bequerel worked with light and the absorption of light by crystals. He also looked at the mechanics of X-rays. His discovery of radioactivity allowed later scientists to perfect the atomic model.
  • J.J. Thomson

    J.J. Thomson
    J.J. Thomson was a very important scientist when it came to the atomic model. Up until his time, all models of the atom looked like a big solild ball. J.J. Thomson discovered the electron, which led him to create the "plum pudding" atomic model. In this model, he thought that the atom was mostly positive, and negative electrons wandered around the atom. The "plum pudding" model influenced other scientists to make better atomic models.
  • Marie "Madame" Curie

    Marie "Madame" Curie
    Marie Curie was a European woman that contributed to atomic chemistry by exploring the mysteries of radioactivity. After radiation was discovered by Henri Baquerel, Marie decided to look further into this discovery. Through this she discovered the elements radium and polonium and won the Nobel Peace Prize for her works in radioactivity. Her discovery later added to the atomic model.
  • Max Planck

    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.
  • Albert Einstein

    Albert Einstein
    Einstein in 1905 also explained the equivalency of mass and energy, expressed by the famous equation e=mc2. Yet these were not sufficient world-changing, revolutionary advances in physics for a single year. Einstein also in 1905 mathematically proved the existence of atoms, and thus helped revolutionize all the sciences through the use of statistics and probability.
  • Robert Millikan

    Robert Millikan
    Robert Millikan was an American scientist that was very interested in J.J. Thomson's finding of the electron (Thomson predicted that the electron was 1000 time smaller than the atom). Millikan wanted to prove this hypothesis. He performed 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
    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.
  • Henry Moseley

    Henry Moseley
    Henry Mosely was an English scientist who worked with Niels Bohr in order to create the real atomic number. Mosely used X-rays to find the frquencies of elements on the periodic table. Before his discovery, the atomic number was just an assigned number to a random element. Mosely used these frequencies to find that the number of protons in the nucleus correlated with the atomic number. This created Mosley's Law.
  • Niels Bohr

    Niels Bohr
    Niels Bohr was a Danish scientist that was a student of Rutherford. He decided to make a new model based off of Rutherford's model, but changed the orbit of the electron. Also, he created energy levels in the atom, where only a certain amount of electrons could fit on one energy level of the atom. Bohr also used Planck's ideas in order to create quantum mechanics, his new concept regarding energy. This model is still used to this day.
  • World War I

    World War I
  • Louis deBrogile

    Louis deBrogile
    Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. He had supported Einstein's ideas and opinions.
  • Erwin Schrodinger

    Erwin Schrodinger
    Erwin Scrhodinger was an Austrian scientist that worked with the Quantum model of the atom. He disagreed with Bohr's theory, so he created his own. He thought that the only way to find the location and energy of an electron in an atom was to calculate its probability of being a certain distance from the nucleus. This equation influenced the Quantum mechanical model of the atom.
  • Werner Heisenberg

    Werner Heisenberg
    Werner Heisenberg was a German scientist that proposed the uncertainties of the Quantum model. He said that you can't know the exact velocity and momentum of the electron at the same time, which means you can't know the exact location of the electron. This principle proves error in Bohr's model because of the uncertainty of the location of an electron.
  • The Great Depression

    The Great Depression
  • James Chadwick

    James Chadwick
    Jame Chadwick was an English scientist that discovered the neutron (before this discovery, Rutherford had concluded that the nucleus was made of positive matter). It made sense that the atom was neutral because the negative electrons and the positive protons cancelled out. But, Chadwick started to question why there was a difference between the atomic mass and the number of protons. Chadwick then found that the missing component was a neutral part: the neutron.
  • World War II

    World War II
    WWII ' >WWII</a>
  • JFK