04CHM114_0123

04CHM114_0123 - CHEM 114A Spring 2004 Fri Jan. 23rd 2004...

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Unformatted text preview: CHEM 114A Spring 2004 Fri Jan. 23rd 2004 Lecture No. 2 fl , Hi \website wwwpublic.asu.edu/~caangell “rt 6! u. d TEE . at . 6"" 1 Mn! 36~1 '1' “a... Slg;£1:canifigures in measurement: careful with calculatorsll) I a fit. “4‘9 . ' '- f' . m...“ “Fa-v.41.“ {u- w: ' u..- and- T'"'\"P Prefixes for reporting measurements alum-:2»... a a m Giga», Inga, kilo-, deci-, centi—, milli-, micro, “3 nano-, pico-, femto- (see table 1.5) we! '2 .t' The typical atom has a diameter of ..... .. Do problems 1.17, 1.19 (8th edition) Dimensional analysis (read section 1.6) Do problems 1.39, 1.41, 1.45 (8‘h edition) Pause for experiments Wag-3; .1 -—__\a__-__ _ CHAPTER 2. Atoms, Molecules, and ions Homework problems: do the red ones and check yourself with the book answers in back. Atomic theory of matter (John Dalton 1803-1807) Building on the law of conservation of mass (total mass remains constant during a chemical reaction in which the nature of the substances change completely) Dalton deduced that matter consists of collections of ATOMS that can combine with each other only according to certain rules. (unlike a solution that can have any proportion of the constituents —e. g sweet vs very sweet coffee). In some substances, called elements, (like mercury, gold sulfur,) all of the atoms are identical. In others the atoms are combined in simple proportions according to a CHEMICAL FORMULA H20 means 1.1.4w M! ff 11's!» it R ‘14! * $W:*d (“'5' fl. 6 ml; «13 o ‘4 H (.2 Law of constant proportions Law of constant proportions In pure compounds the proportions are always the same... Atoms hook together, but only according to how many hooks each atom can have. Different elements can have different numbers of hooks. For instance LiCl vs MgClz, SO2 vs CO r Law of Mu1t1ple p oportions ‘ Q o . a. {I For some combinations of atoms the propfiftionsaefiii change from one set of simple numbers 1:1 , 1:2 etc to another e.g. 1:3 and 2:3 For instance iron and oxygen FeO, Fe203, Manganese MnO, Mn203, MnOz; ' ' In?“ (Multiple proportions but always simple numbers). Finding the ELEMENTS. (substances that could not be further subdivided) flumphrey Davy .... .. Electrolysis of NaCl ...passage of electricity through matter Etc etc (DEMO electrolyte solutions) Atomic Structure The atoms were considered to be INDIVISIBLE BUT Some elements (e. g.Uranium) were found to be decomposing into different elements with the production of He gas, and emission of radiation (Henri Bequerel : radioactivity. 1852-1908) Implies that atoms have subitrgppure WWW Cathode rays and the electron (Demo) High voltage discharge - What is it due to? Charged particles. Negative charge “electrons” SO: Electrons can be emitted from atoms Then the thinking went ........ ..take an electron off an atom and the remaining charged particles can conduct electricity..we remember that Humphrey Davy’s molten salt conducted electricity... it all started to hang together.. Atoms were made up of “stuff” one component of which is electrons. . .negative.. the other stuff must be positively charge to compensate. Sodium atoms + chlorine atoms -) sodium ions (positive) plus chlorine ions (negative).. So sodium itself must have electrons together with something else. It lead to: Thompson, and the “plum pudding” model. 1897 J. J. Thompson magnetic field deflects cathode ray beam. can calculate charge/mass ratio of the particles. ( elm). elm = 1.76 x 108 C/g (C is coulombs...S.I. unit) Then if we can find the charge on the electron, e, we can find its mass, m. Milliken’s oil drop experiment I ‘fl’ - if?“ P: +Qgt‘. '. l." " " ' 4. _ G: l t“ E M" :1 -""’-" e" I \b t ' I bwkn, w"; 3 fl 9""«v3 an?" __—--—x._r_.._. ._. 5 Charge is 1.6 x 10‘19 coulombs (SI unit of charge) Therefore mass of the electron is 1.6 x 10-19 of = 9.13; 10-ng 1.76 X 108 E/g So we arrive at the idea of the simplest atom, hydrogen as consisting of one electron (very light) and one something that is positively charged and much heavier. Rutherford (New Zealand) ...... ..where is the positive charge in an atom?. . . .a test of the plum pudding model. An “atomic bullet” experiment (1910)... see Fig. 2.9 Conclusion: Atoms are mostly empty space. One of our jobs is to understand how that can be, but first. . .Chapter . 3 ...
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This note was uploaded on 11/01/2009 for the course CHM 114 taught by Professor Aksyonov during the Fall '08 term at ASU.

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04CHM114_0123 - CHEM 114A Spring 2004 Fri Jan. 23rd 2004...

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