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Chemistry 100(02) Fall 2013

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  1. Chemistry 100(02) Fall 2013 Instructor: Dr. UpaliSiriwardane e-mail: upali@coes.latech.edu Office: CTH 311 Phone257-4941 Office Hours: M,W, 8:00-9:30 & 11:30-12:30 a.m Tu,Th,F8:00 - 10:00 a.m.   Or by appointment Test Dates: September 30, 2013 (Test 1): Chapter 1 & 2 October 21, 2013 (Test 2): Chapter 3 & 4 November 13, 2013 (Test 3) Chapter 5 & 6 November 14, 2013 (Make-up test) comprehensive: Chapters 1-6 9:30-10:45:15 AM, CTH 328

  2. REQUIRED: Textbook:Principles of Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro - Pearson Prentice Hall and also purchase the Mastering Chemistry Group Homework, Slides and Exam review guides and sample exam questions are available online: http://moodle.latech.edu/ and follow the course information links. OPTIONAL: Study Guide: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd Edition Student Solutions Manual: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro2nd Text Book & Resources

  3. Chapter 2. Atoms and Elements 2.1 Imaging and Moving Individual Atoms…………….. 43 2.2 Early Ideas about the Building Blocks of Matter……. 45 2.3 Modern Atomic Theory and the Laws That Led to It… 45 2.4 The Discovery of the Electron……………………….. 49 2.5 The Structure of the Atom……………………………. 51 2.6 Subatomic Particles: Protons, Neutrons, and Electrons in Atoms……………………………………………… 53 2.7 Finding Patterns: The Periodic Law and the Periodic Table…………………………………………. 58 2.8 Atomic Mass: The Average Mass Of an Element’s Atoms. 64 2.9 Molar Mass: Counting Atoms by Weighing Them……… 66

  4. Chapter 2. KEY CONCEPTS

  5. Periodic Table • Periodic table is an arrangement of all known element according to their atomic number and chemical properties.

  6. Development of Periodic Table Newlands - English Scientist 1864 – Law of Octaves – every 8th element has similar properties

  7. Who is Dmitri Mendeleev? • Mendeleev, Dmitri (1834-1907): Russian chemist • Mendeleev is best known for • his work on the periodic table; • arranging the 63 known • elements into a Periodic • Table based on Atomic Mass

  8. Mendeleev’s Periodic Table the elements are arranged according to increasing atomic weights Missing elements: 44, 68, 72, & 100 amu

  9. Dimitri Mendeleev created this, the original, periodic table.

  10. Predicted Properties of Ekasilicon

  11. Modern Periodic Table the elements are arranged according to increasing atomic numbers

  12. Organization of Periodic Table • Period– horizontal row • Group – vertical column

  13. La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Modern periodic table 1 2 13 1 4 15 1 6 17 18 I A II A III A IV A V A VI A VIIA 0 H He Li Be B C N O F Ne 1 2 3 4 5 6 7 3 4 5 6 7 8 9 10 11 12 III B IVB VB VIB VIIB VIII B IB IIB Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe * Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn + Fr Ra Lr * +

  14. 47 Silver Ag 107.87 Information that may be in the table Atomic number Name of the element Elemental Symbol Average Atomic mass

  15. Vertical columns- groups,families • Horizontal columns- periods • Elements in a group have similar • chemical properties Group IA - alkali metal: Li, Na, K Rb, Cs, Fr Group IIA- alkaline earth metals: Be, Mg, Ca, Sr, Ba, Ra Group VIIA - Halogens: Cl, Br, I, At Group 0 - Noble gases: He, Ne, Ar, Kr, Xe, Rn

  16. A group or family Groups are assigned Roman numerals with an A or B I A II A III A IV A V A VI A VIIA 0 H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar III B IVB V B VIB VIIB VIIIB IB IIB K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Lr La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No

  17. A row or period Periods are assigned numbers H He Li Be B C N O F Ne 1 2 3 4 5 6 7 Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Lr La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No

  18. Periodic Table: Areas = Metal = Metalloid = Nonmetal

  19. Solid Liquid Gas Elemental states atroom temperature He H Li Be B C N O F Ne Cl Na Mg Al Si P S Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe * Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn + Fr Ra Lr * La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No +

  20. The known elements 118 elements are currently known • 89 are metals • 31 are radioactive • 22 are synthetic (all radioactive) • 11 occur as gases • 2 occur as liquids • Let’s take a look at them on the table.

  21. Periodic Table of the Elements

  22. Family Names Group IA alkali metals Group IIA alkaline earth metals Group VIIA halogens Group VIIIA noble gases transition metals inner transition metals • lanthanum series rare earths • actinium series trans-uranium series

  23. What are these? • Transition Metals • Actinides • Lanthanides • Semimetals or Metalloids • Ionic Charges • Poly atomic ions and their charges

  24. Periodic Law • 1) What group or family to the following elements belong to? • a) Na b) Cac) Cld) He

  25. 2) List two elements in each of the following: • a) Main group elements • b) Transition elements • c) Lanthanides d) Actinides

  26. 3) Identify the following elements as either metals, non-metals, metalloids, noble gases, transition metals, actinides or, and lanthanides. • a) Si b) Cac) Cl d) Eu • e) Puf) Ni g) Ar

  27. 4) Which of the following are main group elements? • a) Si b) Ca c) Cl d) Eu • e) Pu f) Ni g) Ar

  28. 31 15 238 92 138 56 P U Ba The atomic symbol & isotopes • Isotopic symbol: atomic symbol showing atomic number (Z) and mass number (A) • Determine the number of protons, neutrons and electrons in each of the following. 2+

  29. Isotopes • *Atoms of the same element but having different masses. • *All isotopes of an element have same atomic number • *Each isotope has a different number of neutrons. • Isotopes of hydrogen H HH • Isotopes of carbon C CC 1 1 2 1 3 1 13 6 12 6 14 6

  30. Isotopes • Most elements occur in nature as a mixture of isotopes. • Element Number of stable isotopes • H 2 • C 2 • O 3 • Fe 4 • Sn 10 • This is one reason why atomic masses are not whole numbers. They are based on averages.

  31. Isotopes & Atomic Mass (Weight) Complete the following table:

  32. Atomic Structure of elemetns • 5) What are isotopes?

  33. 6) How many isotopes does the elemental hydrogen, has? Give their symbols. Are they all these isotopes stable?

  34. 7) Naturally occurring carbon had two stable isotopes (carbon-12 and carbon 13) and an unstable isotope, carbon -14. Write isotopic symbols for • a) carbon-12 b) carbon-13 c) carbon-14: • b) How many protons, neutrons, and electrons are in the carbon-12 isotope?

  35. 8) How many electrons, protons, and neutrons a 24Mg2+ isotope have?

  36. Finding Patterns: The Periodic Law and the Periodic Table • 9) Order of elements in the modern periodic table is arranged according to atomic number. In his periodic table, Mendeleev used atomic weights not atomic numbers. • a) In the periodic table what elements should have been swapped if Mendeleev was to following order of increasing atomic masses strictly? • b) In the periodic table, Why is atomic masses approximately correlated with atomic number?

  37. Finding Patterns: The Periodic Law and the Periodic Table • 9) Order of elements in the modern periodic table is arranged according to atomic number. In his periodic table, Mendeleev used atomic weights not atomic numbers. • c) What is most directly involved in chemical reactivity: nucleus or the outermost electrons? • d) Why do the elements in a group of the periodic table have similar chemical properties?

  38. Average atomic masses • Most elements exits as a mixture of isotopes. • Each isotope may be present in different amounts. • The masses listed in the periodic table reflect the world-wide average for each isotope. • One can calculate the average atomic weight (AAM) of an element if the abundance of each isotope for that element is known.

  39. Masses of Atoms Carbon-12 Scale Masses of the atoms are compared to the mass of C-12 isotope having a mass of 12.0000 amu Atomic mass units (amu)

  40. Mass Spectrometer

  41. MassSpectrum of Neon AAM(Ar) = [(90 x 20) + (10 x 22)] / 100 = 20.20

  42. Atomic Masses andIsotopic Abundances natural average atomic masses = [(atomic mass of isotope)  (fractional isotopic abundance)]

  43. How do you calculate average Atomic Mass? • Ma x a + Mb x b • ------------------------ = AAM • 100 • Ma= mass of isotope a • Mb = mass of isotope b • a = percent abundance of a • b = percent abundance of b • AAM = Average atomic mass (Reported • on the Periodic Table)

  44. How do you calculate average Atomic Mass? Ma x a + Mb x b = AAM Ma = mass of isotope a Mb = mass of isotope b a = fractional abundance of a b = fractional abundance of b AAM = Average atomic mass (Reported on the Periodic Table)

  45. Average atomic masses Example. • Silicon exists as a mixture of three isotopes. Determine it’s average atomic mass based on the following data. • Isotope Mass (u) Abundance • 28Si 27.976 9265 92.23 % • 29Si 28.976 4947 4.67 % • 30Si 29.973 7702 3.10 %

  46. Calculation Gallium in nature consists of two isotopes, gallium-69, with a mass of 69.926 amu and a fractional abundance of 0.601; and gallium-71, with a mass of 70.925 amu and a fractional abundance of 0.399. Calculate the weighted average atomic mass of gallium. 1) Ma x a + Mb x b = AAM Ma x a(%) + Mb x b(%) 2) ----------------------------------- = AAM 100

  47. AAM Calculation • Ma (69Ga ) =68.926 u, • a = percent abundance of 69Ga = 0.601 x 100 • Mb (71Ga ) = 70.925 u, • b = percent abundance of 71Ga = 0.339 x 10 • We can obtain an equation with one unknown, AAM. AAM = 68.926x(0.601 x 100)+70.925 x(0.339x100) 100 AAM (Ga) = 4142.5 + 2829.9 100 AAM (Ga) = 6972.3 = 69.723 100 AAM (Ga) = 69.723 u (amu)

  48. Atomic Mass: The Average Mass of an Element’s Atoms • 10) Silicon exists as a mixture of three isotopes. Determine its average atomic mass based on the following data to correct significant figure. • Isotope Mass (amu or u) Abundance • 28Si 27.976 9265 92.23 % • 29Si 28.976 4947 4.67 % • 30Si 29.973 7702 3.10 %

  49. What is a mole? Chemistry is quantitative in nature; • Its unit is the mole. • The mole as unit vs. “dozen” as an unit • The unit “dozen” is associated with 12 units. • The unit MOLE is associated with 6.02 x 1023 units. • There is Avogadro’s number of units in every mole. • 6.02 x 1023 units is known as Avogadro’s number. • 1 mole = 6.02 x 1023 units • 1 mole of Cu atoms has • an atomic mass of 63.55 g, which is • 6.022 × 1023 Cu atoms, which is approximately 22 pennies.

  50. The Mole • a unit of measurement, quantity of matter present • Avogadro’s Number 6.022  1023 particles • Latin for “pile”