Created by imaniross on Dec 7, 2010
Last updated: 12/09/10 at 08:49 PM
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In 1926 Erwin Schrodinger took atomic models one step further. His creatiion of the quantum theory helped him write and solve a ''Mechanical equation, describing the location and energy" of an electron in hydrogen atom. The Quantum Mechanical Model states that individual electrons don't orbit around the nucleus in exact paths, but instead in an 'electron cloud'. An electron clound indicated the 'probable location of an electron at the given moment'. This theory solved all of great difficulties that troubled the 20th century.
In 1924, Louis DeBroglie had a wave theory. He figured that light is transmitted as waves. This led him to realize that electrons could only exist in atoms if they were in discrete orbits. This helped develop the structure of the atom. His experiments showed that electron beams could be bent as the passed through a slit much like light could.
Soddy worked with Earnest Rutherford to explain that radioactivity is due to the transmutation of elements. They showed that radioactive elements decay into other elements producing alpha, beta and gamma radiation.
Niels Bohr was the first to make the representation of molecular stucture. His idea of what we now call a Bohr Model "Restricts the energy of a system to certain discretevalues" (EBSCO biography, 1). His first contributions to his idea began in 1912. Neils corrected Rutherford's idea by coming up with a new atomic model. The Bohr model "Prevents electrons from falling into the nucleus...it's patterend after the mostion of the planets around the sun, it's ofter referred to as the Planetary model" (Chemistry, Adison-Wesley,362). Niels gathered his first information from rutherford, (Rutherford Model) which is when it was established theexistance of atoms. Downfalls of the Bohr Moodel was that it didn't explain the "Zeenan effect, and interputed poor predictions regarding the spectra of larger atoms" Chemistry, Adison_Wesly, 362). The Quantum Mechanical Model was followed by the Bohr Model. It was an electronic structure of the atom "Asprobility of finding electrons within regions of space"(Chemistry, Adison-Wesley, 363).
Rutherford conducted an experiment in which he shot a beam of positively charged particles into a sheet of gold foil. He also predicted that if atoms were soft, as the plum-pudding model suggested, the particles would pass throught the gold and continue in a straight line. Most of the particles did conitnue in a straight line. However some of the particles were deflected to the sides a bit, and a few bounced straight back. Rutherford realized that the plum-pudding model did not explain his observations. He changed the atomic theory and developed a new model of the atom. Rutherford's model says that most of the atom's mass was in the nucleus. He calculated that the nucleaus was 100,000 times smaller than the diameter of the atom. The atom (Rutherford's theory) was mostly empty space and the electrons traveled in random paths around the nucleus.
Max Planck is considered the inventer of the quantum theory. In 1899 he discovered a new fundaental constat used to calculate energy of a photon, which is the light emitted from an element. When an element is heated, electrons start to move faster and they rise to higher energy levels. when the electrons cool the go back to ground state and emit light. this light is what Max called photons.
Marie Curie discovered radium with her husband. They used radium for nuclear medicine. Radium was used for radioactivity because it killed cancer cells. One characteristic of radium is it can glow in the dark.
In 1897, while working with currents of electricity inside empty glass, Joseph Thomson discovered the electron. He noticed rays, he called "cathode Rays", that were streams of particles smaller that atoms. These rays were made of electrons. He also separated atoms by theur different atomic weights. Earnest Rutherford was able to notice that joseph's ideas werent fully acurate.
Scientist knew that elements combined with each other in specific proportions formed compounds. Dalton claimed that the reason for this was because elements are made of atoms. Dalton published his own three-part atomic theory: 1) All substances are made of atoms. Atoms are small particles that cannot be creatd, divided, or destroyed. 2) Atoms of the same element are exactly alike, and atoms of different elements are different. 3) Atoms join with other atoms to make new sustances. Much of Dalton's theory was correct, but some of it was later proven incorrect later on. Frederick Soddy, another scientist demonstrated the existence of isotopes , which are atoms of an element with different masses.
Democritus thought matter could not be divided indefinately. If you took a piece of matter and broke it in half, then eventually you would no longer be able to break it apart. The smallest particle of matter he named the Atom.
Aristotle claimed that there was no smallest part of matter and that the different substances were made up of proportions of fire, air, earth, and water
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