chm2045ch2 - Chapter 2 Atoms and Elements Dalton's Atomic...

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Unformatted text preview: Chapter 2 Atoms and Elements Dalton's Atomic Theory th Compounds consist of atoms of more than one element combined in particular ratios [Law of Constant Composition and Law of Multiple Proportions] Building up Atomic Structure Benjamin Franklin (1706-1790) discovered two types of electricity, (+) and (-). Henri Becquerel discovered radioactivity in 1896. Pierre and Marie Curie continued that work: atoms disintegrate, i.e., they are divisible. Joseph John Thomson discovered the electron and determined its charge/mass ratio (1896-97). Robert A. Millikan (1909) determined the charge and mass of electron. Ernest Rutherford (1911-19) discovered the proton in a small, dense nucleus. James Chadwick (1932) discovered the neutrons, that are with the protons in the nucleus of atoms. Atomic Structure subatomic particles neutron: no charge, 1.0087 amu, n proton: +1 charge, 1.0073 amu, p+ electron: 1 charge, 0.0005486 amu, e n and p+ packed tightly into dense core called nucleus e distributed more diffusely in space surrounding nucleus dense, central core dense, central core The nuclear atom e n p+ e Radius of atom ~ 100 pm (10 m) Radius of nucleus ~ 0.001 pm Then, if radius of atom was ~ 100 m (a small football stadium), the radius of the nucleus would be ~ 0.001 m = 1 mm 3 atom nucleus 5 Atomic number and Mass number all atoms of a given element have the same number of protons (isotopes) number of protons in an atom given by the atomic number, Z neutral atoms have same number of protons and electrons; Na = 11p+, 11e atoms gain or lose charge by gaining or losing electrons only (not protons!!) total number of protons and neutrons Symbol mass number A charge X Z n element symbol atomic number 23 11 Na + Examples Determine the numbers of electrons, protons, and neutrons in each of the following atoms. 40 18 Ar 40 Ar 18 Z = 18, therefore the atom has 18 p+ A = 40, A = # of p+ + # of neutrons Therefore, # neutrons = A - # p+ 40 18 = 22 neutrons Charge, n = 0, therefore # of e = # p+ = 18 209 82 Z = 82, therefore 82 p+ Pb 2+ A = 209, therefore 209 p+ and n total # neutrons = A - # p+ = 209 82 = 127 n n = 2+, Therefore # e = 82 p+ - 2 = 80 e (lost 2 31 15 P 3 31 3 P 15 Z = 15, therefore 15 p+ 31 3 P 15 Z = 15, therefore 15 p+ A = 31, therefore 31 p+ and n total 31 15 P 3 Z = 15, therefore 15 p+ A = 31, therefore 31 p+ and n total 31 15 = 16 n 31 3 P 15 Z = 15, therefore 15 p+ A = 31, therefore 31 = p+ + n 31 15p+ = 16 n n = 3 , (gained 3 e) - - Isotopes atoms (of same element) that have the same number of protons but different numbers of neutrons, i.e., different A; A X n Z may or may not have same number of electrons 55 52 X 24X 24 _______ 52 X 24 52 3+ 52 X 20 50 Which are Isotopes? X X 24 24 _______ Isotope abundance A sample of naturally occurring sulfur contains several isotopes with the following abundances Isotope % abundance 32S 95.02 33S 0.75 32 S, 33S, 34S, 36S 34S 4.21 16 16 16 16 36S 0.02 The % abundances are determined experimentally. # of atoms of a given isotope % Abundance = x 100 Total # of atoms of all isotopes of element Mass Spectrometry is employed to determine Isotopic Abundances mass spectrometer. Device generates ions that pass down an evacuated path inside a magnet. Ions are separated based on their charge/mass ratio. Mass is, then, calculated. Atomic Mass The atomic mass and Isotope Abundances are determined by means of Mass Spectrometry. Atomic mass of isotope carbon-12 is exactly 12 amu whereas all others of carbon and other elements are referred to that and do not have integer values. 1 1 amu = mass of isotope 12 C = 1.661 10 -24 g 12 % abundance isotope 1 Atomic mass = x (mass isotope 1) 100 % abundance isotope 2 + x (mass isotope 2) + .......... 100 Example Isotope % abundance mass (amu) 64 Zn 48.6 63.9291 66Zn 27.9 65.9260 67Zn 4.1 66.9721 68Zn 18.8 67.9249 70Zn 0.6 69.9253 Example, contd. %abund.i Atomic weight of Zn = mi 100 A.W.= 0.486 63.9291 + 0.279 65.9260 + ... + 0.041 66.9721 + 0.188 67.9249 + ... + 0.006 69.9253 = 65.4 amu Let's name p1 = % of 69Ga and p2 = % of 71Ga. p1 + p2 = 100 then, p1 = 100 - p2 (2) p1 68.9257 + p2 70.9249 AW = 69.723 = then, 100 6972.3 = p1 68.9257 + p2 70.9249. Then, replace p1 by (2) 6972.3 = (100 - p2) 68.9257 + p2 70.9249 6972.3 = 6892.57 - p2 68.9257 + p2 70.9249 6972.3 - 6892.57 = p2 (70.9249 - 68.9257) 6972.3 - 6892.57 p2 = = 39.88% 70.9249 - 68.9257 p1= 100 - p2 = 60.12% Atoms and the Mole The idea of a unit to denote a specific number of items is not new. pair = 2 1 dozen donuts = 12 donuts 1 ream of paper = 500 sheets 1 case = 24 cans Atoms and the Mole A mole is (a collection number) the amount of a substance that contains as many entities as (atoms, molecules, ions, protons, electrons, or other particles) as there are atoms in 12 g of 12C isotope 1 mol = 6.022 x 10 particles = 12 g 12C (Avogadro's number). Amadeo Avogadro Atoms and the Mole 1 mole of ... 1 mole C 1 mole Na 1 mole Au 1 mole H2O molecules 1 mole Na+ Number of particles = 6.022 x 1023 C atoms = 6.022 x 1023 Na atoms = 6.022 x 1023 Au atoms = 6.022 x 1023 H2O = 6.022 x 1023 Na+ ions 1 mole electrons = 6.022 x 1023 electrons Molar Mass The molar mass of any element is the mass in grams of 6.022 x 1023 atoms of that element, i.e., one mole of the element. Molar mass has units of grams per mole (g/mol), and is numerically equal to the atomic weight of the element. Molar mass of Na Molar mass of Cl Molar mass of O = 22.990 g/mol = 1 mole Na = 35.453 g/mol = 1 mole Cl = 15.999 g/mol = 1 mole O Conversion factors Convert moles to mass and Moles to mass g moles x = grams 1 mol Mass to moles 1 mol g x =moles grams The molar mass as conversion factors What is the mass of silicon represented by 0.250 moles of this element? M of Si = 28.086 28.09 g g/mol 0.250 moles x = 7.02 g Si How many moles of manganese are 19.36 g of that metal? M of Mn = 54.938 g/mol 1 mol 19.36 g x = 0.352384 = 0.3524 moles 54.938 g 4 SF How many atoms of calcium are in 4.008 g of that metal? M of Ca = 40.08 g/mol 1 mol 6.022 x 1023 atoms 4.008 g x x 40.08 g 1 mol The density of Au is 19.32 g/cm3. What is the volume of a piece of gold that contains 2.6 x 1024 atoms? If the piece of metal is a square with a thickness of 0.10 cm, what is the length (in cm) of one side of the square? AW = 196.97 g/mol 196.97 g Au What is the average mass of one germanium atom? M Ge = 72.59 g/mol Divide the mass of a mole by the number of atoms in that mole. 1 mole Ge = 72.59 g = 6.02 x 1023 atoms 72.59 g Ge 1 mol Ge g Ge x = 1.205 x10-22 1 mol Ge 6.022 x1023 atoms Ge 1 atom Ge 0.0000000000000000000001205 g !!!!!!! Review Example How many atoms are in 1.50 mol Na? a.1.50 b. 9.03x1023 c. 3.00 d. 2.49x10-24 e. 345 6.022 1023 atoms 1.50 mol = 9.03 x 1023 atoms 1 mol How many moles of Ar in 5.22 x 1022 atoms of this noble gas? a. 11.5 b. 0.0867 c. 1.15x1022 d. 8.67x1023 e. 3.14 x 1046 1 mol 5.22 x 1022 atoms = 0.0867 mol 6.022 1023 atoms Review Example What is the mass (grams) of one atom of Na? a. 22.99 b. 0.04350 c. 3.818 x 10-23 b. 2.619x1022 1 mol Na 22.99 g = 3.818 x 10-23 g/atom 6.022 1023 atoms Periodic Table(*) a listing of the elements arranged according to their chemical and physical properties elements are arranged according to similar properties. Groups or families contain elements with similar properties in vertical columns. periods are horizontal rows of elements. Every period has a number (row) from 1 through 7. (*) originally Mendeleev by atomic mass (1869), later Moseley by increasing atomic number (1913). Periodic Table Groups referred to by number or top element some have names: The Representative Elements alkali metals - group 1A alkaline earth metals - group 2A noble gases - group 8A halogens - group 7A chalcogens - group 6A pnictogens - group 5A Alkali Metals Group 1A(1), the alkali metals, includes lithium, sodium, potassium, rubidium, cesium, and francium ChemNow 2.17 Exercise Halogens Group 7A(17) the halogens, includes fluorine, chlorine, bromine, and iodine. Representative Elements 1 1A 1 1 18 8A 2 H 1.008 3 2 2A 4 13 3A 5 10.81 13 26.98 31 69.72 49 114.8 81 204.4 14 4A 6 12.01 14 28.09 32 72.59 50 118.7 82 207.2 15 5A 7 14.01 15 30.97 33 74.92 51 121.8 83 209.0 16 6A 8 16.00 16 32.07 34 78.96 52 127.6 84 (210) 17 7A 9 19.00 17 35.45 35 79.90 53 126.9 85 (210) 4.003 10 20.18 18 39.95 36 83.80 54 131.3 86 (222) He Ne Ar Kr Li Na K 39.10 37 85.47 55 132.9 87 (223) Be Mg Ca Sr 3 3B 21 44.96 39 88.91 57 138.9 89 (227) 4 4B 22 5 5B 23 6 6B 24 7 7B 25 8 8B 26 55.85 44 101.1 76 190.2 108 Uno (265) 61 (147) 93 (237) 9 8B 27 58.93 45 102.9 77 192.2 109 Une (266) 62 150.4 94 (242) 10 8B 28 58.69 46 106.4 78 195.1 11 1B 29 12 2B 30 B C N P O F 6.941 9.012 11 12 22.99 19 24.31 20 40.08 38 87.62 56 137.3 88 (226) Al Si S Cl Sc Y Rb Cs Fr 47.88 50.94 40 41 91.22 92.91 72 73 178.5 104 Ti V Cr Cr Zr Nb Ta 52.00 98 54.94 42 43 95.94 74 183.8 106 Mn Tc Fe Co Rh Ir Ni Mo W (98) 75 186.2 107 Uns (262) 60 144.2 92 238.0 Ru Os Pd Pt 63.55 65.39 47 48 107.9 79 197.0 Cu Ag Zn Ga In Ge As Se Te Br I 112.4 80 200.6 Cd Hg Sn Sb Bi Xe Ba La Hf 180.9 105 Re Au Tl Pb Po At Rn Ra Ac Unq (257) Unp 58 (260) Unh 59 (263) 63 152.0 95 (243) 64 157.3 96 (247) 65 158.9 97 (247) 66 162.5 98 (249) 67 164.9 99 (254) 140.1 90 232.0 Ce Th 140.9 91 (231) Pr Nd U Pm Np Sm Pu Eu Gd Tb Dy Cf Ho 68 69 168.9 101 (256) 70 173.0 102 (254) 71 175.0 103 (257) 167.3 100 (253) Er Tm Yb Lu Pa Am Cm Bk Es Fm Md No Lw Transition Elements 1 1A 1 1 18 8A 2 H 1.008 3 2 2A 4 13 3A 5 10.81 13 26.98 31 69.72 49 114.8 81 204.4 14 4A 6 12.01 14 28.09 32 72.59 50 118.7 82 207.2 15 5A 7 14.01 15 30.97 33 74.92 51 121.8 83 209.0 16 6A 8 16.00 16 32.07 34 78.96 52 127.6 84 (210) 17 7A 9 19.00 17 35.45 35 79.90 53 126.9 85 (210) 4.003 10 20.18 18 39.95 36 83.80 54 131.3 86 (222) He Ne Ar Kr Li Na K 39.10 37 85.47 55 132.9 87 (223) Be Mg Ca Sr 3 3B 21 44.96 39 88.91 57 138.9 89 (227) 4 4B 22 5 5B 23 6 6B 24 7 7B 25 8 8B 26 55.85 44 101.1 76 190.2 108 Uno (265) 61 (147) 93 (237) 9 8B 27 58.93 45 102.9 77 192.2 109 Une (266) 62 150.4 94 (242) 10 8B 28 58.69 46 106.4 78 195.1 11 1B 29 12 2B 30 B C N P O F 6.941 9.012 11 12 22.99 19 24.31 20 40.08 38 87.62 56 137.3 88 (226) Al Si S Cl Sc Y Rb Cs Fr 47.88 50.94 40 41 91.22 92.91 72 73 178.5 104 Ti V Cr Cr Zr Nb Ta 52.00 98 54.94 42 43 95.94 74 183.8 106 Mn Tc Fe Co Rh Ir Ni Mo W (98) 75 186.2 107 Uns (262) 60 144.2 92 238.0 Ru Os Pd Pt 63.55 65.39 47 48 107.9 79 197.0 Cu Ag Zn Ga In Ge As Se Te Br I 112.4 80 200.6 Cd Hg Sn Sb Bi Xe Ba La Hf 180.9 105 Re Au Tl Pb Po At Rn Ra Ac Unq (257) Unp 58 (260) Unh 59 (263) 63 152.0 95 (243) 64 157.3 96 (247) 65 158.9 97 (247) 66 162.5 98 (249) 67 164.9 99 (254) 140.1 90 232.0 Ce Th 140.9 91 (231) Pr Nd U Pm Np Sm Pu Eu Gd Tb Dy Cf Ho 68 69 168.9 101 (256) 70 173.0 102 (254) 71 175.0 103 (257) 167.3 100 (253) Er Tm Yb Lu Pa Am Cm Bk Es Fm Md No Lw Colors of solutions of Transition Metal Compounds Inner Transition Elements 1 1A 1 1 18 8A 2 H 1.008 3 Li Be Mg Ca Sr 3 3B 21 44.96 39 88.91 57 138.9 89 (227) 4 4B 22 5 5B 23 6 6B 24 7 7B 25 8 8B 26 55.85 44 101.1 76 190.2 108 Uno (265) 61 9 8B 27 58.93 45 102.9 77 192.2 109 Une (266) 62 10 8B 28 58.69 46 106.4 78 195.1 11 1B 29 12 2B 30 2 2A 4 13 3A 5 10.81 13 26.98 31 69.72 49 114.8 81 204.4 B 14 4A 6 6.941 9.012 11 12 22.99 19 Na K 24.31 20 40.08 38 87.62 56 137.3 88 (226) Al 12.01 14 28.09 32 72.59 50 118.7 82 207.2 C 15 5A 7 14.01 15 30.97 33 74.92 51 121.8 83 209.0 N P 16 6A 8 Si 16.00 16 32.07 34 78.96 52 127.6 84 (210) O 17 7A 9 19.00 17 35.45 35 79.90 53 126.9 85 (210) F 4.003 10 20.18 18 39.95 36 83.80 54 131.3 86 (222) He Ne Ar Kr S Cl 39.10 37 85.47 55 132.9 87 (223) Sc Y Rb Cs Fr 47.88 50.94 40 41 91.22 92.91 72 73 178.5 104 Ti V Cr Cr Zr Nb Ta 52.00 98 54.94 42 43 95.94 74 183.8 106 Mn Tc Fe Co Rh Ir Ni Mo W Ba La Hf (98) 75 Ru Os Pd Pt 63.55 65.39 47 48 107.9 79 197.0 Cu Ag Zn Ga In Ge As Se Te Br I Ra Ac Unq 180.9 105 (257) Unp 58 (260) Unh 59 (263) 186.2 107 Uns (262) 60 Re Au 112.4 80 200.6 Cd Hg Sn Sb Bi Xe Tl Pb Po At Rn 140.1 90 232.0 Ce Th 140.9 91 (231) Pr 144.2 92 238.0 Nd U (147) 93 (237) Pm Np 150.4 94 (242) Sm Pu 152.0 95 (243) Eu 63 157.3 96 (247) Gd 64 158.9 97 (247) Tb 65 162.5 98 (249) Dy Cf 66 164.9 99 (254) Ho 67 68 167.3 100 (253) Er 168.9 101 (256) Tm 69 173.0 102 (254) Yb 70 71 175.0 103 (257) Lu Pa Am Cm Bk Es Fm Md No Lw Metal/nonmetal gradual transition in properties from metallic to nonmetallic moving from left to right across a row [Row 3: Na (s) Ar(g)] o nonmetallic to metallic down a group [Grp 4A: C Pb Malleable: can be hammered or pressed into new shapes (coins, rings, etc.) Ductile: can be pressed, beaten, or drawn into shape when cold (wires, such as Cu) solid at room temperature (except for Hg) luster photoelectric effect (e emission due to light) thermionic effect (e emission due to heat) readily lose electrons good thermal and electrical conductors Metals Nonmetals solid, liquid, or gas brittle if solid (fracture) non-malleable, non-ductile thermal and electrical insulators do not exhibit photoelectric effect do not exhibit thermionic effect readily gain electrons Metalloids (Semimetals) properties intermediate between those of metals and nonmetals are located table around the solid ladder between metals and nonmetals in periodic B, Si, Ge, As, Sb, Te, Po, At Noble gases Are the least reactive elements Are gases, none-abundant on Earth, but He is the second in the universe after hydrogen Neon in advertising signs Some lasers are made of He, Ar, Kr Learning Check Identify each of the following elements as 1) metal 2) nonmetal 3) metalloid A. sodium B. chlorine C. silicon D. iron E. carbon F. antimony ____ ____ ____ ____ ____ ____ Example Match the elements to the description. A. Metals in Group 4A(14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn B. Nonmetals in Group 5A(15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb C. Metalloids in Group 4A(14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb Example The elements magnesium and calcium are in what group? a. alkali metals b. alkaline earth metals c. halogens d. noble gases Which pair of elements are nonmetals? a. sodium and potassium b. magnesium and barium c. boron and aluminum d. carbon and bromine Identify the period number for the row that ends in argon. a. Period 1 b. Period 2 c. Period 3 d.Period 4 Example Which statement is characteristic of metals? A. Shiny. B. Poor conductors of electricity. C. High melting temperatures. a. statement A only b. statements A and B only c. statements A, B, and C d. statements A and C only Which statement is false? A. Potassium is an alkali metal. B. Strontium is an alkaline earth metal. C. Argon is a noble gas. D. Zinc is a halogen. Example What is the right order of increasing metallic character for the elements Rb, F, P, Ga? a) Rb < F < P < Ga b) P < F < Rb < Ga c) Ga< Rb < P < F d) F < P < Ga < Rb ...
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