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Historical development of atomic theory
Historical development of atomic theory
Historical development of atomic theory
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The Evolution of the Atomic Theory
The five atomic theorys of the past two centuries represent the sudden
advancement of science in modern times. Begining with a basic theory on the
behavior of atoms to the current model, some changes have been made, and
some ideas are still the same. Ancient Greek philosophers belived that
everything was made up of invisible particles called atmos. Since then the
theory of atoms did not progress untill 1803.
John Dalton was the first scientist to compose a theory of matter based
on atoms. Dalton's atomic theory is based on four concepts. He stated:
"1. All elements are composed of atoms, which are indivisable and
indestructable particles.
2. All atoms of the same element are exactly alike; in particular, they
have the same mass.
3. Atoms of different elements are different; in particular, they have
different masses.
4. Compounds are formed by the joining of atoms of two or more
elements." 1
All of Dalton's ideas account for the laws of definate and multiple
proportions and the law of conservation of mass. Some of Dalton's points are
still thought to be true, but over time this origional theory has been modifyed.
The first of these modifications came in 1897 when J.J. Thomson discovered
the electron. Based on the work of William Crookes and his "Crookes tube"
(Cathode-ray tube), Thomson discovered a negative charged particle was the
cause of the light produced by the cathode-ray tube. He also discovered that
these particles are present in all elements. These cathode-ray particles are
now known as electrons. Soon after the discovery of electrons the proton
was discovered. This led Thomson to conclude that ther were an equal
number of both particles present in the atom.
Twelve years later Lord Ernest Rutherford was experimenting with
alpha particles. He shot a stream of them at a peice of gold foil surrounded
by zinc-sulfide. When an alpha particle strikes ZnS it produces a flash of
light. The particles mostly stayed in a constant stream through the foil, but a
few were deflected. This led Rutherford to belive that there must be a small,
dense cluster of protons in the middle of the atoms to deflect the small
number of particles.
Neils Bohr was the next physicist to advance the atomic theory. He
explained what Rutherford could not about how the electron could stay in
orbit around the nucleus. When the electron has little energy it is closer to the
nucleus, when it absorbs more energy it travels farther from the nucleus.
There is a definate number of electrons that can be in the same orbit. When
the orbits closest to the nucleus are filled the atom is at a ground state.
Although the atomic theory was developed in increments, George Johnston Stoney is most famous for contributing the term electron: fundamental unit quantity of electricity. Stoney would develop the concept fourteen years before he coined the term electron. He also made contributions to the theory of gasses, cosmic physics, and estimated the number of molecules in a cubic millimeter of gas.
Atoms are electrically neutral; the electrons that bear the negative charge are equal in number to the protons in the nucleus
The atomic bomb1 is the most destructive weapon known to mankind. A bomb of this nature is capable of obliterating anything up to four square miles and anything reaching outside that area receives very extreme damage. Albert Einstein was the man who had convinced the United States to research the Atomic Bomb.
The Big Bang Theory is one of the most important, and most discussed topics in cosmology today. As such, it encompasses several smaller components that attempt to explain what happened in the moments after creation, and how the universe we know today came from such a fiery, chaotic universe in the wake of the Big Bang. One major component of the Big Bang theory is nucleosynthesis. We know that several stellar phenomena (including stellar fusion and various types of super novae) are responsible for the formation of all heavy elements up through Plutonium, however, after the advent of the Big Bang theory, we needed a way to explain what types of matter were created to form the earliest stars.!
Protons are positively charged and electrons are negatively charged. Protons and electrons both have charges of equal magnitude (i.e. 1.602x10-19 coulombs). Neutrons have a neutral charge, and they, along with protons, are the majority of the mass in an atom. Electron mass, though, is negligible. When an atom has a neutral charge, it is stable.
he found the number of alpha particles emitted per second by a gram of radium.
I chose the books titled, “Thirty Years That Shook Physics,” by the quite illustrious Dr. George Gamow for my third quarter physics related book review. George Gamow certainly lived up to his own name by his depth of knowledge in his various explanations of the most productive thirty years in Physics history throughout the novel. The two hundred paged book George Gamow wrote, which covers ten complete chapters of detailed analyzes of the basic laws of physics and why these various laws made this time period the most productive years in physics history. Though since my quarter two physics related book review was by Dr. George Gamow also, I will not be getting into a biographical sketch of
To understand what a radioactive isotope is a basic understanding of the atom is necessary. Atoms are comprised of three subatomic particles : protons, neutrons and electrons. Protons and neutrons bind together to form the nucleus of the atom, while the electrons surround and orbit the nucleus. Protons and electrons have opposite charges and therefore attract one another (electrons are negative and protons are positive, and opposite charges attract), and in most cases the number of electrons and protons are the same for an atom (making the atom neutral in charge). The neutrons are neutral. Their purpose in the nucleus is to bind protons together. Because the protons all have the same charge and would naturally repel one another, the neutrons act as "glue" to hold the protons tightly together in the nucleus.
2 electrons. The second electron shell can contain at most 8 electrons.
The electrons circling the nucleus experience Coulomb force due to the difference in their electric charge. When a material is put in an external magnetic field, these electron experience an additional force, known as the Lorentz force, from the magnetic field. This force may result either in the increase of centripetal force on the electrons hence pulling them towards the nucleus, or it may result in the decrease of the centripetal force on the electron hence pulling them away from the nucleus, depending on the direction in which the electrons are orbiting. In accordance with Lenz’s law, this effect will increase the orbital magnetic moments that were aligned opposite to the applied field and decrease the orbital magnetic moments that were aligned parallel to the external magnetic field. This results in a small net magnetic moment, acting in the direction opposite to the applied magnetic
To start off, learning the Bohr-Rutherford diagrams in grade nine was a very big confusion for me. I had never fully understood how many shells should go around the nucleus nor did I know how to do the many calculations. As I progressed into grade ten, the teachings became easier. The review shows an example such as in the the bohr diagram, a nucleus is in the center, which is a little circle, and following that there are shells surrounding it containing electrons. Each ring can only hold a certain amount of electrons, and so the first shell around the nucleus can hold a maximum of 2 electrons, the next shell is able to hold a maximum of 8 electro...
New inventions are created daily; however, it is those that truly change the world that are remembered. The use and discovery of atomic energy negatively impacts the world because of the danger it entails. Many people across the world believe that the use of atomic energy is a mistake based off of past events that have occurred such as the bombings at Hiroshima and Nagasaki. The abuse of atomic energy has been proven to damage society’s morale, population and could potentially destroy entire populations.
Physics began when man first started to study his surroundings. Early applications of physics include the invention of the wheel and of primitive weapons. The people who built Stone Henge had knowledge of physical mechanics in order to move the rocks and place them on top of each other. It was not until during the period of Greek culture that the first systematic treatment of physics started with the use of mechanics. Thales is often said to have been the first scientist, and the first Greek philosopher. He was an astronomer, merchant and mathematician, and after visiting Egypt he is said to have originated the science of deductive geometry. He also discovered theorems of elementary geometry and is said to have correctly predicted an eclipse of the sun. Many of his studies were in astronomy but he also observed static electricity. Phythogoras was a Greek philosopher. He discovered simple numerical ratios relating the musical tones of major consonances, to the length of the strings used in sounding them. The Pythagorean theorem was named after him, although this fundamental statements of deductive geometry was most likely first an idea from Egyptian methods of measurements. With the help of his followers he discovered that the earth was a sphere, but he did not believe it revolved around the sun.
For this work, Rutherford won the 1908 Nobel Prize in chemistry. In 1909, now at the University of Manchester, Rutherford was bombarding a thin gold foil with alpha particles when he noticed that although almost all of them went through the gold, one in eight thousand would "bounce" (i.e., scatter) back. The amazed Rutherford commented that it was "as if you fired a 15-inch naval shell at a piece of tissue paper and the shell came right back and hit you."
The idea of a world progressing, or evolving, in science hasn’t been around forever. In fact, the Enlightenment period in the seventeen hundreds with scientists such as Isaac Newton the man who discovered gravity, Louis Pasteur the chemist who invented the vaccine to prevent rabies, Charles Darwin the father of evolution, Benjamin Franklin the first scientist to toy with the dangers and possibilities of electricity, and so many more wonderful scientists was the start of the “progress” that revolutionized our world. Of the scientists who progressed our world, few shaped modern biology the way Charles Darwin managed to. Thomas Kuhn saw the progress people like Darwin made not as truth seeking, but simply as filling in another piece of the puzzle of science, challenging the very definition of the Scientific Revolution. After reviewing Kuhn’s idea of science, Darwin appears to play a substantial role in the paradigm shift from the science of old to new. Kuhn looked at Darwin and saw science evolve much as Darwin’s organisms appeared to evolve