CHE 131 Lecture Notes 09-10-07

# CHE 131 Lecture Notes 09-10-07 - AN ION Sum of the number...

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CHE 131 Lecture Notes 09/10/07 Uncertainty and Significant Figures 500> 1 sig figs (ambiguous example) 500. > 3 sig figs 5.0 x 10^2 > 2 sig figs ADDING> 17.245 + 0.1001 = 17.3451 WHICH ROUNDS TO 17.345 (lowest decimal point = 3, which is what the answer is rounded to) Sci-notation> same rules apply > is sometimes easier to see sig figs with Multiplying/dividing> look at total # of sig figs, go with the lowest one Rounding> 37.663147 to 3 sig figs becomes 37.7 If it is 37.65, then you can just round up if you want to 37.7 Atomic Numbers and Mass Numbers Atomic # Z tells us the # of protons, and also the # of electrons if it is an ATOM, NOT

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Unformatted text preview: AN ION! Sum of the number of protons and neutrons in an atom is = A = mass number, which is the approximate mass of an atom in amu *Z is constant for a given element 63Cu29> 29 protons and 29 electrons; 63-29 = 34 neutrons 25Mg > 12 protons and 12 electrons; 25-12 = 13 neutrons 27Al > 13 protons and 13 electrons; 27-13 = 14 neutrons 1 amu = 1/12 of the mass of the atom that contains 6 protons and 6 neutrons 1 amu- = some obscure number of grams CHE 131 Lecture Notes 09/10/07...
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CHE 131 Lecture Notes 09-10-07 - AN ION Sum of the number...

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