200px stylised lithium atom

Timeline of the Atom

  • 348

    Aristotle

    Aristotle
    Aristotle was one of the most influential Greek philosophers. He made his discovery is 348/347 B.C. He rejected the concept of the atom. He didn't believe that atoms moved through empty space because he didn't think empty space existed. He got so many people to agree with him that no one challenged it for two thousand years.
  • 400

    Democritus

    Democritus
    Democritus was a Greek phosopher that lived between 460-370 B.C. He contruibuted to the Atomic Theory in 400 B.C. He was the first person to propose the idea that matter was not infinitely divisible. He believed matter was made up of tiny individual particles which he called atomos, or atoms. He also believed that atoms could not be created, destroyed, or further divided.
  • Antoine Lavosier

    Antoine Lavosier
    Antoine Lavoisier was a French scientist who was one of the first to use an analytical balance to monitor chemical reactions. He studied the thermal decomposition of mercury oxide. Lavoisier is recognized as the father of modern chemistry. He performed some of the first quantitative chemical experiments. His data and observations led to the law of conservation of mass.
  • Revolutionary War

    Revolutionary War
    The Revolutionary War started in 1775 because the 13 colonies didn't like being under British control. They were angry at Britain so they declared their independence from them and the war started. The Americans won the war and became free in 1783. A main reason the British lost was because they needed to conserve resources.
  • Joseph Proust

    Joseph Proust
    Joseph Proust reasearched and declared that a substance has the same composition where ever or how ever it was made. He discovered that the same substance found in different locations had the same elements at the same ratio. He came up with the law of definite proportions. The law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created.
  • John Dalton

    John Dalton
    John DaltonJohn Dalton was a schoolteacher from England that made the beginning of the development of modern atomic theory. He revised Democritus's ideas based on scientific research he conducted. His Atomoic Theory was that all matter is composed of extremely small particles called atoms and all atoms of a given element are identical. He also stated that atoms cannot be created, divided into smaller particles, or destroyed and that in a chemical reaction, atoms are separated, combined, or rearranged.
  • Amedeo Avagadro

    Amedeo Avagadro
    Amedeo AvogadroAmedeo Avagadro was an Italian physicist. During his time he did not use the word atom, he used molecule. He is famous for his contributions to theory of moles and molecular weight, including what is known as Avagadro's law. The number of molecules in one mole is called is called Avagadro's number. He theorized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
  • William Crookes

    William Crookes
    William Crookes was an English physicist. He was instrumental in discovering the cathode ray which led to one of the most important technological inventions of the 20th century which is the television. Television and computer monitor images are formed as radiation from the cathode strikes liglht-producing chemicals that coat the backside of the screen.
  • Civil War

    Civil War
    The Civil War lasted from 1861 to 1865, and was a war between the American states. The war was over slavery and the north and south fought each other. The north was against slavery while the south was for it. Over 600,000 soldiers died and a lot of land was destroyed in the south. After the war was over the process to get blacks equal rights began.
  • Alexander Graham Bell

    Alexander Graham Bell
    Alexander Graham Bell invented the telephone. He was very interested in the education of deaf people. This led him to create the microphone and then the telephone. His invention spread all over the country and even throughout Europe. The first telephone call was made in Connecticut. Long distance connections were made between Massachusetts and New York. The telephone has come a long ways now today.
  • Henri Becquerel

    Henri BecquerelHenri Becquerel was a French physicist. He studied minerals that emit light after being exposed to sunlight which was called phosphorescence. He wanted to determine whether phosphorescent minerals also emitted X rays. Along the way he accidnetally discovered that phosphorescent uranium salts, even when not exposed to light, produced spontaneous emissions that darkened photographic plates.
  • J.J. Thomson

    J.J. Thomson
    J.J. Thomson was an English physicist who determined that there are particles smaller than the atom. He proved Dalton's atomic theory wrong and figured out atoms were divisible into smaller subatomic particles. He identified the first subatomic particle, the electron.
  • Madame Curie

    Madame Curie
    Marie Curie and her husband Pierre took Becquerel's mineral sample and isolated the components emitting the rays. They concluded that the darkening of the photographic plates was due to rays emitted specifically from the uranium atoms present in the mineral sample. Curie named the processs by which materials give off such rays, radioactivity.
  • Spanish American War

    Spanish American War
    The Spanish American War only lasted four months. It lasted from April 25, 1898, to August 12, 1898. Most of the fighting took place in or near Cuba and the Philippines. The reasons the United States went in this war was because of a couple different reasons including the Cuban struggle for independence and the sinking of the U.S. warship, Maine. This war firmly established the US as a major military power.
  • Max Planck

    Max Planck
    Max PlanckMax Planck was a German physicist who looked for an explanation as to why heated objects emitted light. His study led to a conclusion that matter can gain or lose energy only in small, specific amounts called quanta. This was a big discovery since before scientists had believed that energy could be absorbed and emitted in continually varying quantities with no minimum limit.
  • Airplane

    Airplane
    The inventors of the airplane were Orville and Wilbur Wright. They worked on inventing this for a long time and eventually they had their first successful flight on December 17, 1903. The airplane carried a man, rose by its own power, flew naturally and at even speed, and descended without damage. They would keep improving the airplane after this.
  • Albert Einstein

    Albert Einstein
    Alvert Einstein proposed that electromagnetic radiation has both wavelike and particlelike natures. He etended Planck's idea of quantized energy and claculated that a photon's energy dpends on its frequency. He also proposed that the energy of a photon of light must have a certain minimum, or threshold, value to cause the ejection of photoelectron.
  • Robert Millikan

    Robert Millikan was an American physicist who determined the charge of an electron. The charge he measure around 100 years ago is within 1% of the current accepted value. He calculated the mass of a single electron by knowing the electron's charge and using the known charge-to-mass ratio.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest RutherfordErnest Rutherford was a scientist involved in an experiment called the plum puding model which he proved to be incorrect. He then developed a new atomic model which showed that most of an atom consists of electrons moving rapidly through empty space and that they are held together because of their atrraction to the positive charged nucleus.
  • Henry Moseley

    Henry Moseley
    Henry Moseley was an English scientist who discovered that atoms of each element contain a unique positive charge in their nuclei. He also found out that by arranging the elements in order of increasing atomic number instead of increasing atomic mass solves the problems with the order of the elements on the periodic table. His arrangement of elements by atomic number resulted in a clear periodic pattern of properties.
  • Niels Bohr

    Niels Bohr
    Niels Bohr was a Danish physicist that worked in Rutherford's laboratory. He proposed a quantum model for the hydrogen atom that seemed to answer why the elements atomic emission spectra is discontinuous rather than continuous. His model correctly predicted the frequencies of the lines in hydrogen's atomic emission spectrum. He proposed that the hydrogen atom has only certain allowable energy states. He also related the hydrogen atom's energy states to the motion of the electron within the atom.
  • World War I

    World War I
    World War I lasted from July 28, 1914, to November 11, 1918. The war was the Central Powers against the Allied Powers. The Central Powers consisted of Germany, Austria-Hungary, and Turkey while the Allies were Great Britain, France, Russia, Italy, and the US. Nine million soldiers were killed and 22 million were wounded. The war started after the assassination of the Archduke Franz Ferdinand of Austria.
  • Louis de Broglie

    Louis de Broglie
    Louis de Broglie was a French graduate student in physics. He propsed an idea that eventually accounted for the fixed energy levels of Bohr's model. He developed an equation for the wavelength of a particle of mass moving at velocity. Broglie predicted that all moving particles have wave characteristics. His equation shows why it works.
  • Werner Heisenberg

    Werner Heisenberg
    Werner HeisenbergHeisenberg was a German theoretical physicist who concluded that is is impossible to make any measurement on an object without disturbing the object at least a little. He came up with the Heisenber uncertainty principle that stated that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time.
  • Erwin Schrodinger

    Erwin Schrodinger
    Erwin Schrodinger was an Austrian physicist who furthered the wave-particle theory proposed by de Broglie. He derived an equation that treated the hydrogen atom's electron as a wave. His model for the hydrogen tom seemed to apply equally well to atoms of other elements unlike Bohr's model. The difference between his and Bohr's model what that his quantum mechanical model made no attempt to describe the electron's path around the nucleus.
  • James Chadwick

    James Chadwick
    James Chadwick was Rutherford's coworker. He was an English physicist who showed that the nucleus also contained another subatomic particle, the neutron. He stated that the neutron had a mass almost equal to a proton, but it carried no electrical charge. By now they had come up with the three subatomic particles, the electron, proton, and neutron. Together those account for all of the mass of an atom.
  • World War II

    World War II
    World War II lasted from 1939 to 1945. This second war was even more devistating than the first. Adolf Hitler rose to power from Germany and started Nazi concentration camps. He didn't like Jewish people so they were sent to these awful camps and forced to work and go to these death camps where they lined people up and killed them. Around 45-60 million people were killed, 9 million being Jewish.
  • Microwave Oven

    Microwave Oven
    The microwave was accidentally discovered by Percy LeBaron Spencer. He found that radar waves had melted a candy bar in his pocket. He found this out years later after two scientist invented the magnetron. The first microwave oven to be sold was as large and as heavy as a refridgerator today.
  • Vietnam War

    Vietnam War
    The Vietnam War lasted a long time, from 1954 to 1975. The war included North Vietnam and its southern allies against South Vietnam and their main help, the United States. The war began after Ho Chi Minh rose to power. More than three million people, which included 58,000 Americans, died in the war. The war created divisions back in the US among citizens. The war ended after communist forces siezed control of Saigon in 1975.
  • 9/11

    9/11
    On Semptember 11, 2001, know as 9/11, a tradegy happened. American Airline planes were taken over by Islamic terrorists. They flew the planes they hijacked into the World Trade Center as well as the Twin Towers. A fourth plane was headed to the White House but passengers on the flight took control of the plan and crashed it in a field. Many people died that day and 9/11 will never be forgotten.