Created by sari_o on Feb 28, 2011
Last updated: 03/05/11 at 03:02 PM
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Current models researched and developed by today's scientists are much more complicated than all the atomic theories and models that were hypothesized and designed by the four main scientists. Although it was not only the four who came up with ideas for the atomic theory and model, they all contributed to the information we all have now. With the addition of their information, scientists today believe that there are even smaller particles than neutrons and protons called quarks. They also believe that there are more than three subatomic particles. It is likely that the atomic theory will evolve for a long period consisting with new experiments, observations, and discoveries. Sources: Science 10, p.20-21 If interested, please listen to the Atom Song
He was married to Margrethe Nørlund in 1912, and had six sons, but unfortunately lost two. The other four have achieved to different professions. Died in Copenhagen, Bohr was a very educated individual who contributed to the atomic theory. Although scientists today are searching for more information about what an atom really looks like, people like students who are studying atoms, elements, and compounds look at Bohr's model today.
Bohr also was an leading advocate of international co-operation in developing peaceful uses of atomic energy.
J.J. Thomson had influenced many people like scientists after his death to keep studying about the atomic concepts. Because of his discovery of electrons, this helped many other scientists to discover new information in all their areas of research. Although Thomson's father intended his to become an engineer, he became a well known physicist instead. He was married to Rose Elisabeth in 1890, the daughter of Sir George E. Paget, K.C.B. They had a son named Sir George Paget Thomson who became the Emeritus Professor of Physics at the London Uniservity, and was awarded the same nobel prize as his father (Nobel prize for Physics) in 1937. They also had one daughter. Source: http://nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.html http://www.chemheritage.org/discover/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx Check both out if interested!
Rutherford was an inspiring leader of the Cavendish Laboratory because he helped many people to aim for their greatest achievements. Some won Nobel prizes because of his help! Rutherford has also published many books that involved chemistry too. Some of Rutherford's chief recreations were golfing and motoring.
He was married to Mary Newton, the daughter of Arther and Mary de Renzy Newton. They had one child named Eileen who married to R.H Fowler.
He died in Cambridge and honourably buried in Westminster Abbey, just west of Sir Isaac Newton's tomb and by that of Lord Kelvin.
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This instrument helped Bohr to prove that different elements have different colour combinations. It is because each spectrum is produced by light with a certain energy. This reinforced Bohr's atomic theory's key feature of energy levels of electrons.
Since Bohr was questioning about Rutherford's "Solar System" atom, he decided to come up with his own model. Rutherford's theory did not make sense because if electrons were spiralling around the nucleus, the electrons would collide into the nucleus and the atom would collapse. Also electrons moving around a nucleus should constantly emit energy in the form of light or radiowaves, but it only happens when electrical energy is supplied to them. So Bohr found out that each elements emits specific colours of light, so he used spectroscopes and and mathematics to discovered that atoms have energy levels (electron shells). This way it made sense: the electrons are able to add and subtract unlike protons, and have certain allowed energies that keeps the atom stable. Plus, they could not exist between energy levels. For example, he came up with the rule where in energy level 1, there is only a maximum of 2 electrons, and for energy level 2, there could only be 8 or less.
Rutherford observed the deflection of alpha particles that were deflected from the gold foil shown in the picture. There were collisions of gold atoms that caused alpha particles to change direction slightly and hit different areas of the fluorescent screen placed around the foil. Most alpha particles went straight through the foil, but interestingly some did not make it through. This proved that alpha particles are more massive than electrons. He discovered that each atom contains a nucleus and an empty space that is larger than the nucleus. He finalized that most alpha particles can pass through the foil by passing within the individual atoms, but not between them. His hypothesis about neutrons also explained the existence of isotopes too.
Source: Science 10, p.18
Video: Rutherford's Experiment: Nuclear Atom
Did you know that in 1904, Hantaro Nagaoka, a Japanese scientist proposed a similar atomic model as Rutherford's? Nagaoka's model showed a disk-shaped atom that had negative particles orbiting the positively charged nucleus. If Nagaoka's model was correct, Rutherford mentioned in 1911 that his model would be also correct. Source: Science 10, p.17
Key points of Thomson's Atomic Theory: - Electrons are less massive than atoms - Electrons are present in all samples of matter - Electrons are negatively charged - Therefore, each atom would have positive charges Thompon's Plum Pudding Model: - Positively charged sphere that has constantly emitting fast-moving, positively charged particles (called alpha particles) having 7200 times the mass of an electron - Contains sufficient numbers of electrons - Both charges balance each other - Also called the "Raisin-Bun" **Thomson did not discover neutrons Source: Science 10, p.16
Thomson's new version of the gas discharge tube helped him collect the direct evidence of cathode rays and their streams of negatively charged particles. He created the new version of the tube by using charged plates to bend the cathode rays around a curved path. He obtained this evidence by measuring the radius of their path so he could calculate the information about the charge and mass of the particles. He was able to work between the charge and the mass of negatively charged particles in a quantitative relationship. He discovered that each electron has less than 1/2000 the mass of a single hydrogen atom. His experiment worked out as... 1. A source of high-energy electricity connected the cathode and anode 2. When the electricity turned on, the current produced a cathode ray that beamed to the anode 3. Because the anode had a a slit in the center, a narrow beam was produced 4. After the narrow beam was bent by a positive and negative plate Source: Science 10, p.15
"At first there were very few who believed in the existence of these bodies smaller than atoms. I was even told long afterwards by a distinguished physicist who had been present at my lecture at the Royal Institution that he thought I had been pulling their legs." Source: Science 10, p.15
Niels Henrick David Bohr was born in Copenhagen as the son of Christian Bohr who was the Professor of Physiology at the Copenhagen University at that time. Growing up in an atmosphere around intelligent people has shaped his interest in physiology. He has recieved lots of education, plus have met and worked with Sir J.J.Thomson and Professor Rutherford in Manchester. He also has won the Nobel Prize in Physics in 1922, but importantly, Bohr discovered that different atoms have different energy levels.
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Also check out the video "Niels Bohr"
Ernest Rutherford was another scientist who contributed to the history of the atomic theory. He was born in New Zealand and studied with J. J. Thomson at Cambridge. After he taught at the McGill University in Montreal than won the 1908 Nobel Prize in Chemistry. But most importantly, he designed his "Solar System" atomic model.
Source: Science 10, p.16
Check out the link or video "The Discovery of the Atomic Nucleus Part 3 of 15" for more information if interested!
Joseph John Thomson was a British physicist who discovered the electron when he was studying cathode rays in gas discharge tubes. It was not only Thomson who was studying the same area, but he made his own atomic theory: The Plum Pudding Model
He was sometimes called "the father of the electron".
Thomson was born on Dec 18th, 1856, at Cheetham Hill, Manchester. He enrolled in many schools like the Trinity College, and ended becoming a Cavendish Professor of Experimental Physics at Cambridge, London. Because Thomson was interested in physics, he had produced many textbooks with the help of others people, won many awards and prizes (including the Nobel Prize in Physics 1906), and importantly, came up with his own atomic theory.
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Also take a look at the video "The Discovery of Electrons Part 2 of 15"
New inventions and improvements of technology helped scientists to find their discoveries. The gas discharge tube was improved by a German glass blower and mechanic Heinrich Geissler. His tubes produced cathode rays which helped scientists to lead several experiments to infer that matter contains tiny particles that have negative charges. Source: Science 10, p.13
Dalton passed away at Manchester, England. He was buried at the Ardwick Cemetery, Ardwick, Lanshire, England. Although he was never married, he lived with friend Rev. W. Johns (1771-1845), in George Street, Manchester for more than 25 years.
With the help of his predictions, many other scientists improved the research of the atomic theory for high accuracy. With his discovery, people today are still looking for more answers about the science behind the atomic theory.
Source: (The link)
If interested, there is more detailed information about John Dalton's life from this link:
Dalton predicted that the atom was a solid, uniform sphere like a billard ball. He also predicted that every substance is made up of indivisible atoms. Dalton's Atomic Theory: 1. All matter is made up of small particles called atoms 2. Atoms cannot be created, destroyed, or divided into smaller particles 3. All atoms of the same element are identical in mass and size, but they are different in mass and size from the atoms of other elements. 4. Compounds are formed when atoms of different elements combine in fixed (definite) proportions 5. Chemical reactions change the way atoms are grouped, but the atoms themselves are not changed in reactions Source: Science 10, p.12-13
Since there was no gas discharge tubes back when he studied about atoms, Dalton used measurements made by a French chemist named Joseph Proust (1754-1826). This lead Dalton to think that an atom of oxygen would have eight units as its mass. Since Dalton's predictions were mostly assumption, there were some incorrect. For example, he assumed that atoms are combined simply so he guessed the formula for water as OH. Source: Science 10, p.13 Photo shows the correct chemical formula: H2O
Born in Eaglesfield, Cumberland, England.
Dalton was an English scholar and teacher who published his comprehensive atomic theory in 1808.
He lived in England, and had a father named Joseph Dalton, a mother named Deborah Greenup, a brother named Jonathan and a sister named Mary. During his residence, he discovered from many things from his observations and experiments. He kept a diary of 200, 000 meteorological observations for 57 years!
Science 10 (Plus the link)
If interested, take a look at the John Dalton video.
(Around 400 BC) Discovered the theory of atomism: -All matter is made of infinite numbers of solid atoms in constant motion -Atoms differ in shape and texture -The word "atoms" originated from the Greek word "atomos", meaning indivisible If interested, check out the video Democritus.