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History of the Atomic Structure
Transcript of History of the Atomic Structure
Robert Millikan made his discovery about the atomic structure of electricity in 1910.
He discovered a way to find the charge of an electron using the oil drop experiment.
He proved that the mass of an electron is 1000x smaller than the smallest atom.
This was only a few years before WWI started.
He discovered that energy is made a tiny particles which he called quanta, and that each quantum's energy is related to the frequency of radiation.
His experiment took place in around 1900.
Marie Curie and her husband discover radium in 1898.
The Spanish-American War is declared in 1898.
Year Rutherford's experiment was led to a better model.
Max Planck did his main experiment in 1900.
The same year the 2nd Modern Olympic Games took place in Paris, France.
In 1907 Earnest Rutherford made his discovery about the mass of atoms.
Robert Millikan proved the atomic structure of electricity in 1910.
Halley's comet was passing Earth in 1910 as well.
Henry Moseley experimented in 1913, the same year Woodrow Wilson became President.
Marie Curie was born on November 7th of 1867.
Robert Millikan was born March 22nd of 1868.
October 20th 1891 James Chadwick is born.
James Maxwell dies on November 5th 1879.
Earnest Rutherford was born August 30th 1871.
Ellisa Bragaw - James Chadwick, James Maxwell, Marie Curie
Rachel Letellier - Robert Millikan, Max Planck, Henry Mosely
Sara Buyanovsky - J.J. Thomson, Antoine Lavoisier, Neils Bohr
Sky Coleman - Ernest Rutherford
Robert Millikan died on December 19th, 1953.
Max Planck died October 4th 1947.
James Chadwick dies on July 24th, 1974.
Marie Curie dies at age 66 on July 4th of 1934.
James Chadwick conducts his experiments in 1932.
The Great Depression is occurring.
Earnest Rutherford died October 19th 1937.
Oil Drop Experiment
The oil drop experiment used an atomizer to spray a mist of oil droplets. Some of them fell through the upper floor reaching terminal velocity. Using a formula he calculated the mass of each drop. He then applied eclectic charge to the falling drops using x-rays. The electrons then became charged to the oil drops. Attached battery plates created a voltage that acted on the charged oil drops causing just the right ones to be suspended in midair.
James Chadwick was the first person to discover the presence of the neutron. James conducted a series of experiments in which he projected alpha particles through beryllium. The particles which went through the beryllium ended up being neutrons. James then put the neutrons through paraffin wax which then adds another type of particle, protons.
James Maxwell is born on June 13th 1831.
Max Planck was born April 23rd 1858.
Henry Moseley experimented in 1913.
He developed x-ray specters which allowed him to further study atomic structure.
As a result he was able to sort the periodic table of elements in order of their atomic number.
James Maxwell theorized of electromagnetism in which if there is presence of a positively charged particle, there would be a negatively charged particle too.
Marie Curie discovered radioactivity and the fact that the nucleus of an atom can be unstable. She and her husband discovered radium, an unstable and radioactive element which showed that not all elements are unbreakable.
JJ Thomson was born December 1856.
JJ Tomson died August 30, 1940.
J.J. Tomson suggested that atoms have parts. He said the idea that cathode rays are really streams of very small pieces of atoms. Three experiments led to this conclusion.
Experiment 1: He built a cathode ray tube ending in a pair of metal cylinders with a slit in them. He wanted to see by bending the rays with a magnet, if he could separate the charge from the rays. The electrometer did not register much electric charge if the rays were bent so they would not enter the slit. He noticed negative charge and the cathode rays must somehow be stuck together meaning you cannot separate the charge from the rays.
Experiment 2: All the attempts at bending the rays by Thomson and other scientist were failed attempts. He noticed charged particle will normally curve as it moves through an electric field, but not if it is surrounded by a conductor. He thought of an idea, taking great pains to extract nearly all of the gas from a tube, and found that now the cathode rays did bend in an electric field after all.
Experiment 3: He wanted to determine the basic properties of particles. He collected data using a variety of tubes and using different gases. He then calculated the ratio of the mass of a particle to its electric charge (m/e).
Results: Thomson said "we have in the cathode rays matter in a new state, a state in which the subdivision of matter is carried very much further than in the ordinary gaseous state: a state in which all matter... is of one and the same kind; this matter being the substance from which all the chemical elements are built up."
Around January 15, 1892 - James Naismith publishes the rules of basketball and the first official game of basketball is held five days later at the YMCA in Springfield, Massachusetts.
Antoine Lavoisier is best known for his reformation of chemical nomenclature, including composing the first extensive list of elements. Mostly famous for terming both Oxygen and hydrogen after discovering the two gases. Know to many as the father of chemistry.
Antoine Lavoisier was born August 26, 1743.
Antoine Lavoisier dies May 8, 1794.
By 1777 Lavoisier had concluded that combustion, or burning, is the chemical union of the burning substance with a gas that he named oxygen. The first to recognize the importance of accurately weighing the substances used in experiments.
Through some experiments on humans, Lavoisier determined that carbon dioxide and water are given off during respiration. Lavoisier also investigated problems of heat, fermentation, and the liquefaction of gases.
During this time the Boston Massacre began around 1770.
Neils Bohr was born October 7, 1885.
Neils Bohr dies November 18, 1962.
He studied under J. J. Thomson, who discouraged his ideas, and under Ernest Rutherford, whose work was expanded by Bohr into a new theory on the structure of the atom in 1913.
He said that electrons travel in fixed orbits around the atom's nucleus, and further explained how electrons emit or absorb energy
He said outer orbits hold more electrons than inner orbits, that atoms traveling from one orbit to another emit tiny amounts of radiation, and that these orbits determine chemical properties of an atom.
Bohr proposed that the outer orbits could accommodate more electrons than the inner orbits.
During this time, Elvis was the king of rock n roll.
Henry Moseley was born November 23rd 1887.
The Gold Foil Experiment
Rutherford studied the effects x-rays on different materials. After the discovery of radioactivity, he started studying the compounds and particles of uranium metals. Rutherford found that if you coat a screen with zinc sulfide, it would create a flash of light each time it was hit by a particle. Geiger, Rutherford assistant, would sit in the dark until his eyes were adjusted. Then they would count the flashes. He later found a narrow beam of negative particles was thinned out when passing through a thin film of metal.
This later lead to the conclusion that when the foil was filled with negative particles he found the order was small on one degree.