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Download The Structure of Atoms - Zachary Toben
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ELRN 385 By Hunter Kopff, Monte Meyerink, and Zachary Toben Describe the evidence for the existence of electrons, protons, neutrons, and describe the properties of these subatomic particles. Discuss atoms of different elements in terms of their numbers of electrons, protons, and neutrons, and define the terms atomic number and mass number. Experiments by scientists in the mid 19th century led to a change in the atomic theory by Dalton. ◦ This stated that atoms were indivisible and indestructible. They discovered that atoms could be broken down into pieces after all. These pieces are called subatomic particles. The three most important subatomic particle are the electron, proton, and neutron. Electrons were discovered by using cathode (electricity) rays by J.J. Thomson. ◦ He figured out that these rays had a negative charge, since the cathode rays came from the negatively charged cathode. ◦ He also figured that the cathode rays consisted of tiny particles that were hitting the paddles of the wheel. His experiments showed that a cathode ray consisted of particles that have a mass and charge of -1. Their mass is very small compared to the nucleus. Electron symbol: eElectrons exist on the edge of atoms in different shell levels. Since scientists learned that electrons were negatively charged and atoms had no charge, there must have been part of the atom that contained some positive charges. Rutherford used the gold foil experiment to figure out that there was a space in the atom that was very dense, concentrated, and positively charged. This region of the atom was called the nucleus. Nucleus has all of the positive charge of the atom, nearly all of its mass, but only a small fraction of the volume of the atom. Nucleus is in the center of the atom. A proton is a positively charged particle (charge of +1) and symbolized by p or p+ The charge of a proton was calculated to be equal in magnitude but opposite in sign to the charge of an electron. Proton’s mass is 2000 times the mass of an electron. Since protons and electrons together did not account for the whole mass of the atom scientist searched for another subatomic particle. This particle had to be neutral since the electron charge and proton charge canceled each other out. Neutrons were discovered by James Chadwick by using a beam through alpha particles. Neutrons have a charge of 0 and neutrons are almost exact same mass as the protons. Symbolized by N. Where are the protons, neutrons and electrons located? What are the charges of each subatomic particle? What are the relative masses of each particle in regard to the total mass of the atom? Atomic Number- the number of protons that an atom has. ◦ Hydrogen has an atomic number of one since it only has one proton. ◦ Ex- Carbon ◦ Ex- Mercury ◦ Ex- Plutonium Mass Number- is equal to the total number of particles in the nucleus (protons + neutrons). ◦ Helium has a mass number of 2 , one proton and one neutron. ◦ Ex- Lead ◦ Ex- Gold ◦ Ex- Bromine Describe the evidence for the existence of electrons, protons, neutrons, and describe the properties of these subatomic particles. Discuss atoms of different elements in terms of their numbers of electrons, protons, and neutrons, and define the terms atomic number and mass number.
