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CHEMISTRY - CHAPTER 4 AND 10 - ATOMIC THEORY I. IT Introduction : early theories on what matter is made up of. A. 400 B.C. - Democritus. 1. _______________________ 2. things were made up of indivisible particles which he called atoms - _________________ _______________________________________ 3. rough atoms - ______________________ smooth atoms - _____________________ 4. atoms of everything existed. 5. since atoms of everything exist, this does not allow for chemical reactions. B. Aristotle = 384 - 322 B.C. 1. ______________________________ a. 4 elements = ____________________ 1. these were really all the same thing called _____________ 2. THIS THEORY WAS VERY MUCH ACCEPTED BECAUSE WAS NOT AS ABSTRACT AS DEMOCRITUS' WAS! 3. also does not allow for chemical reactions. C. II. late 1700s = Lavoisier and Priestly. 1. dealt with air and water. 2. separated air into ___________________ 3. separated water into _________________. 4. Lavoisier. a. conducted a reaction in a closed system. b. proved that ________________________ __________________________________ c. made up of indivisible particles - this led to the ______________________ _________________________. D. Proust. 1. dealt with fool's gold. 2. broke down into ______________________. 3. broke water down into hydrogen and oxygen. 4. his work led to the _________________ _____________________________ a. __________________________________ ______________________________________ Dalton's Atomic Theory - 1803. A. beginning of modern chemistry. B. his theory - back to Democritus' theory. 1. 2. 3. 4. 5. C. This theory allows for chemical reactions, which leads to a lot of progress in chemistry. III. Dalton's Law of Multiple Proportions. A. He predicted this law. B. C. Dalton's atomic theory was the first scientific model:_______________________________ 1. 2. 3. IV. V. VI. Gay-Lussac. A. Discovered that volumes of reacting gasses and their products ____________________________ ________________________________________ B. example. 2 H2 (g) + O2(g) ----> 2 H2O (g) C. example. N 2 + 3H2 ---> 2NH3 ________________________________________ Avogadro. A. equal volumes of gases (at same temp, pressure) have _____________________________________ 1. this discovery led to the discovery of the gas laws. 2. one mole of any gas at 0 C and 1 atmosphere of pressure is ___________________ (now we can use this in stoichiometry problems!) a. 1 atmosphere Atomic Particles. A. Electrons. 1. discovered in a cathode ray tube : vacuum with oppositely charged ends. 2. _______________ - discovered them in 1897. a. determined the charge/mass ratio of this particle. 3. _______________ - oil drop experiment to determine the actual charge of the electron. a. e- = ___________________________ b. we say that the e- has 1 unit of electric charge. 4. mass of e- = 1/1837 of H atom. = 1/1836 of a proton. = ____________amu =_____________grams B. Protons. 1. discovered by _____________ when he used a modified cathode ray tube. a. found that there were rays travelling in the opposite direction from the electrons. 2. found that the charge on these particles was positive and equal in size to the electron. 3. the proton has 1 unit of positive charge. 4. mass = 1837 times that of an electron. 5. mass of proton is 1 amu C. VII. Neutron. 1. discovered by _______________________ 2. essentially same mass as proton. ( 1 amu) 3. no charge. Atomic Mass and Atomic Number. A. Atomic Mass. 1. almost all of the mass of an atom is located in the nucleus. 2. atomic masses measured in a.m.u. a. 1 amu = 1/12 mass of C 12 atom. (6 n, 6 p+, 6 e-) b. a C 12 atom has a mass of exactly 12 amu, the standard for amu. 3. usually chemists deal in moles - use Avogadro's number to convert amu to grams. ( ________________________) B. Atomic Number. 1. the number of protons in an element is called the atomic number of the element (Z). 2. the number of protons determines what element it is. 3. number of e- = number of p+ in a neutral atom. 4. number of neutrons _____________________ 5. for this reason, the masses of all of the atoms in an element are not the same. 6. the reported atomic mass of an element is the _______________________________________ 7. 8. 9. the protons and neutrons are called _________ because they're in the nucleus. mass number = number of nucleons (A). number of neutrons = _________________ Example: In Silicon atoms: 92.21% have a mass of 27.97 amu 4.70% have a mass of 28.976 amu 3.09% have a mass of 29.974 amu. What is the average atomic mass of Silicon? Example: In the Francium atom with mass number 220, how many protons, neutrons, and electrons are there?