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Name_______________________________________________Class______________Date___________ 1 Antonelli – Chemistry –LHWHS 2010-2011 Review Packet – Unit 2 – Intro to Atomic Structure Review Packet – Unit 2 Intro to Atomic Structure History of Atomic Theory 1. Compare and contrast Dalton, Rutherford, and Thomson's theories on atomic structure and the experiments they used to develop their theories. You should be able to answer an essay question on this topic. Dalton Dalton's Atomic Theory (early 1800s) 1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. Thomson - 1897 In 1897, J. J. Thomson dramatically changed the modern view of the atom with his discovery of the electron. Thomson's work suggested that the atom was not an "indivisible" particle as John Dalton had suggested but, a jigsaw puzzle made of smaller pieces. Thomson's notion of the electron came from his work with a nineteenth century scientific curiosity: the cathode ray tube. For years scientists had known that if an electric current was passed through a vacuum tube, a stream of glowing material could be seen; however, no one could explain why. Thomson found that the mysterious glowing stream would bend toward a positively charged electric plate. Thomson theorized, and was later proven correct, that the stream was in fact made up of small particles, pieces of atoms that carried a negative charge. These particles were later named electrons. Thomson imagined that atoms looked like pieces of plum pudding, a structure in which clumps of small, negatively charged electrons (the "raisins") were scattered inside a smear of positive charges. In 1908, Ernest Rutherford, a former student of Thomson's, proved Thomson's plum pudding structure incorrect.: Name_______________________________________________Class______________Date___________ 3 Antonelli – Chemistry –LHWHS 2010-2011 Review Packet – Unit 2 – Intro to Atomic Structure Rutherford – 1908 Ernest Rutherford developed his atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. Rutherford came to this conclusion following the results of his famous gold foil experiment. This experiment involved the firing of radioactive particles through minutely thin metal foils (notably gold) and detecting them using screens coated with zinc sulfide. Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'. Rutherford’s theory replaced the previously held “plum pudding” model of the atom. Atomic Structure and How We Represent it 2. Be able to determine the number of protons, neutrons and electrons in an atom given the atom's atomic mass and atomic number. Remember: atomic number = # of protons Atomic mass = # protons + # of neutrons # of neutrons = atomic mass – atomic number 3. Describe the model of the atom, ion, or isotope in terms of protons, neutrons, and electrons Neutrons and protons form a dense, positively charged nucleus. Electrons are very small negatively charged particles that move in orbitals surrounding the nucleus; these orbitals are often referred to as an “electron cloud”. 4. Be able to express an atom’s, isotope’s, or ion’s Name_______________________________________________Class______________Date___________ 5 Antonelli – Chemistry –LHWHS 2010-2011 Review Packet – Unit 2 – Intro to Atomic Structure composition using the following format: , 5. State a relative mass, size, and charge of an electron, proton, and neutron. Protons and neutrons have approximately the same mass. Electrons are about 2000 times smaller than protons or neutrons. 6. Understand how atomic structure is represented on the periodic table. You should be able to find the atomic number and atomic mass of an element from the periodic table. 7. Identify a given element as a metal or a non-metal based on it’s location in the periodic table 8. Locate and identify the following groups on the periodic table: a. Halogens b. Alkali Metals c. Alkaline Earth Metals d. Transition metals e. Noble Gases 9. Given the number and kind of atoms that make up a compound, write the chemical formula it. Each molecule of this compound contains two hydrogen atoms and one oxygen molecule H2O Each unit of this compound has 1 calcium for every 2 chlorines CaCl2 Average Atomic Mass 10. Demonstrate understanding of the difference between mass number and average atomic mass by calculating average atomic mass using experimental evidence. Refer to your Pennium lab and isotope homework for more information on how to do this (it involves calculating a weighted average) Ions 11. Compare and contrast the difference in atomic structure of an ion, isotope, and neutral atom. Ion = charged particle (atom with different number of electrons than protons) Isotope = Atoms of an element with same number of protons but different numbers of neutrons. This lends a different mass number to each isotope. Neutral atom = atom with same number of electrons and protons 12. Know how to use the terms cation and anion Cation = positively charged ion Anion = negatively charged ion Name_______________________________________________Class______________Date___________ 7 Antonelli – Chemistry –LHWHS 2010-2011 Review Packet – Unit 2 – Intro to Atomic Structure 13. Be able to predict the ion an atom will most likely form based on its location in the periodic table. Fluorine is in group 17 – thus it is most likely to gain an electron and form FOxygen is in group 16 – so it is most likely to gain two electrons and from O2Sodium is in group 1 – so it is most likely to lose one electron and form Na+ Calcium is in group 2 – so it is most likely to lose 2 electrons and form Ca2+