Ch 3 Student Notes

# Ch 3 Student Notes - 1 Ch 3 Atomic Structure and the...

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1 Ch 3 Atomic Structure and the Periodic Table Figure 3.1 size relationship is not to scale, ratio of average diameters atom/nucleus = 10 5

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2 Atoms are very small and spherical. Radii Range 0.9 x 10 -10 to 2.4 x 10 -10 m 90 – 240 pm Recall Figure 1.12 Atomic Mass example: 1 H atom = 1.673 x 10 -24 g 1atomic mass unit (amu) = 1.6605 x 10 -24 g For H: 1.673 x 10 -24 g x 1 amu . 1.6605 x 10 -24 g = 1.008 amu
3 Ch 3.1 Internal Structure of an Atom Subatomic particles An atom is characterized by the number of protons ( p ) that it contains. A proton has a positive electrical charge. p charge = 1.60 x 10 -19 coulombs = +1 relative charge p mass = 1.6726 x 10 -24 g = ______ amu A neutron ( n ) has no charge associated with it. n mass = 1.6750 x 10 -24 g = ______ amu An electron ( e ) has a negative electrical charge. e charge = - 1.60 x 10 -19 coulombs = -1 relative charge e mass = 9.109 x 10 -28 = _________ amu mass of p ~ mass of n >>> mass of e - mass of e - is often ignored

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4 Ch 3.2 Atomic Number and Mass Number Atomic number = Z = # of protons (unique physical property of each element) Mass number = A = # of protons + # of neutrons # of neutrons = ___________ For a neutral atom, net electrical charge = zero # of electrons = # of protons = _____ A E complete chemical symbol notation Z
5 A 23 E Na Z 11 # p = Z = ____ # n = A Z = ________ = ____ # e - = # p = ____

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6 Ch 3.3 Isotopes and Atomic Masses Isotopes are atoms of an element that have the same number of protons and electrons but different numbers of neutrons. 12 13 14 C C C 6 6 6 isotopes have nearly identical chemical properties most elements have at least two isotopes
7 Table 3.2 Elements with Z = 1 through 12 The atomic mass of an element is the calculated weighted average mass for the isotopes.

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8 Chem 101 Grading Scheme Quizzes 180 points 180/1000 = 0.18 Labs 160 points 160/1000 = 0.16 Exams 660 points 660/1000 = 0.66 1000 1.00 Sample calculation of weighted average Quizzes 85 % x 0.18 = 15.3 % Labs 95 % x 0.16 = 15.2 % Exams 55 % x 0.66 = 36.3 % Average ___% ____ % Weighted Average
35 37 Cl Cl 17 17 34.96885 amu 36.96590 amu 75.77 % 24.23 % natural abundance atomic mass of Cl = weighted average mass for the isotopes 34.96885 x 75.77/100 = 25.60 36.96590 x 24.23/100 = 8.957 35.46 amu 63 65 Cu Cu 29 29 62.9298 amu 64.9278 amu Atomic weight Cu = 63.546 amu Which isotope is the more abundant? Answer:

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## This note was uploaded on 06/03/2011 for the course CHM 123 taught by Professor Woodward during the Fall '08 term at Ohio State.

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Ch 3 Student Notes - 1 Ch 3 Atomic Structure and the...

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