CHM 1020 Final: Chapter 2 Short Study Guide

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Florida State University
Chemistry and Biochemistry
CHM 1020

Chapter 2- Atoms and Elements Short Study Guide Explain Millikan’s oil drop experiment and how it led to the measurement of the electron’s charge. Why is the magnitude of the charge of the electron so important? Millikan created a measurement machine that placed electrons in an oil drop and sprayed them with ionizing radiation, thus giving the drops negative charges. The lower part of the plate was negative as well, so the drops were able to slowed down from their gravity fall and even reversed (because like charges repel each other). This experiment led to discover the process of measuring electrons because Millikan found he could calculate the size of the electric field required to halt the freefall of the drops and also figure out the drops’ mass (determined by their radii and density). Finally, the magnitude of the mass is important because it determines how strongly an atom holds its electrons. If atoms held their electrons more loosely they would most likely not be stable, but if they held their electrons too tightly there would be less compounds or none at all, therefore, life would not be possible. Describe Rutherford’s gold foil experiment. How did the experiment show that the plum- pudding model of the atom was wrong? Rutherford created an experiment that was to determine the structure of an atom. Since it was discovered that electrons are present in an atom and that they are negatively charged. Since it was assumed that atoms are neutral and electrons are negatively charged, there should be some positive charged inside it that makes it neutral. Rutherford work under the discoveries and assumptions of an atom which was plum pudding model. According to the model there were negatively charged particles and electrons suspended or embedded in a sphere of positive charge. The experiment of plum pudding was wrong because Rutherford worked with particles through gold foil, and he found that most of the particles went through, some went to different directions or others deflected back towards the source and because of this he state that this experiment was incorrect. What defines an element? Its atomic number, in other words the number of protons it contains in the nucleus. State the periodic law. How did the periodic law lead to the periodic table? The periodic law states as follows: “ When the elements are arranged in order of increasing mass, certain sets of properties recur periodically.” Because of these recurring properties Mendeleev decided to organize the known elements in horizontal rows by order of increasing mass (from left to right) and arranged the rows so that elements with similar properties fall in the same vertical columns. What are the characteristic properties of each of the following groups? a. Noble gases: Mostly unreactive (8A) b. Alkali Metals: All reactive metals (1A) c. Alkaline earth metals: Fairly reactive (2A) d. Halogens: Very reactive nonmetals (7A) Why is the mass corresponding to a mole of one element different from the mass corresponding to a mole of another element? The mass of one element different from the mass of another element because of the chemical structure of each element. All elements are composed of the subatomic particles of protons, neutrons and electrons, and also the mass corresponding to a mole varies with atoms. An automobile gasoline tank holds 21kg of gasoline. When the gasoline burns, 84kg of oxygen is consumed, and carbon dioxide and water are produced. What is the total combined mass of carbon dioxide and water that is produced? According to the Law of Conservation of Mass, the total mass of reactants equals the total mass of the products. Then, if gasoline and oxygen have 21 kg and 84 kg making a total of 105 kg, then the mass of carbon dioxide and water must be 105 kg. How many electro
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