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CHEM115 General Chemistry I

CHEM115 General Chemistry I. Contacting me: dmyton@lssu.edu & Pronto Homework: http://edugen.wiley.com Register your ID with Wiley, then enter your book code

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CHEM115 General Chemistry I

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  1. CHEM115 General Chemistry I • Contacting me: dmyton@lssu.edu & Pronto • Homework: http://edugen.wiley.com • Register your ID with Wiley, then enter your book code • WileyPLUS: RESOURCESReading content      Chapter Opener      2.1 Elements and Atoms are Described by Dalton's Atomic Theory      2.2 Atoms are Composed of Subatomic Particles      2.3 The Periodic Table is used to Organize and Correlate Facts      2.4 Elements can be Metals, Nonmetals, or Metalloids      2.5 Formulas and Equations Describe Substances and their Reactions      2.6 Molecular Compounds Contain Neutral Particles Called Molecules      2.7 Ionic Compounds are Composed of Charged Particles called Ions      2.8 The Formulas of Many Ionic Compounds can be Predicted      2.9 Molecular and Ionic Compounds are Named following a System      Summary      Tools for Problem Solving      Questions, Problems, and Exercises      Glossary       • Office Hours Videos      Chapter 2, Problem 76      Chapter 2, Problem 83      Chapter 2, Problem 99a      Chapter 2, Problem 99b      Chapter 2, Problem 99c      Chapter 2, Problem 104a      Chapter 2, Problem 104b      Chapter 2, Problem 104c      Chapter 2, Problem 104d      Chapter 2, Problem 104e      Chapter 2, Problem 120a      Chapter 2, Problem 120b      Chapter 2, Problem 120c      Chapter 2, Problem 120d      Chapter 2, Problem 120e      Chapter 2, Problem 120f      Chapter 2, Problem 120g      Chapter 2, Problem 129      Chapter 2, Problem 130      Chapter 2, Problem 132      Chapter 2, Problem 138       • ChemFAQ      ChemFAQ - Chapter 2       • Interactive LearningWare      2.86. Interactive LearningWare      2.88. Interactive LearningWare       • Video Demonstrations      Sodium and chlorine       • Additional Resources      3D Molecules      Audio Pronunciation Guide

  2. Ch 2. Elements, Compounds and Chemical Reactions Brady & Senese, 5th Ed.

  3. Chemical Laws • The law of conservation of mass - in a chemical reaction, the mass of the reactants (starting materials) will equal the mass of resulting products • Implication: reactions involve the re-organization of materials. • The law of definite proportions- the ratio of masses of each element is fixed for a given compound • Implication: Each atom has a fixed specific mass, thus in unique combinations, the mass ratio is specific 2.1. Elements and atoms are described by Dalton’s atomic theory

  4. Learning Check: Magnesium burns in oxygen to form magnesium oxide. If 16.88 g of Mg are consumed and 28.00 g of MgO are produced, what mass of oxygen was consumed? 2.1. Elements and atoms are described by Dalton’s atomic theory

  5. Question: Two compounds of copper and chlorine exist with one having twice as much chlorine per gram of copper as the other. This is evidence of which law? a: Conservation of Mass b: Definite Proportions c: Multiple Proportions

  6. + Dalton’s Atomic Theory • Matter consists of tiny particles called atoms • Atoms are indestructible. In chemical reactions, the atoms rearrange but they do not themselves break apart 2.1. Elements and atoms are described by Dalton’s atomic theory

  7. NaCl has a 1:1 atom ratio on the atomic level and larger Dalton’s Atomic Theory (Cont.): • In any sample of a pure element, all the atoms are identical in mass and other properties. • The atoms of different elements differ in mass and other properties. • In a given compound the constituent atoms are always present in the same fixed numericalratio. 2.1. Elements and atoms are described by Dalton’s atomic theory

  8. John Dalton

  9. Learning Check: In a sample of MgO, there are 16.89 g Mg and 11.11 g O. What mass of O would there be in a sample that contains 2.00 g of Mg? 2.1. Elements and atoms are described by Dalton’s atomic theory

  10. Your Turn! In a sample of an unknown compound, the mass ratio of Cl to C is 47.227g Cl to 4.00 g C. In another sample, there are 0.553 g of Cl. What mass of C would be in this sample? • 0.1532 g • 6.52 g • 0.153 g • 0.0468 g • None of these 2.1. Elements and atoms are described by Dalton’s atomic theory

  11. Question: 9 grams of water contain 1 gram of hydrogen. How many grams of water contain 3 grams of hydrogen? a: 1/3 gram b: 3 grams c: 9 grams d: 27 grams

  12. The Law Of Multiple Proportions When two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. • cements the idea that atoms react as complete (whole) particles. • chemical formulas indicate whole numbers of atoms- not fractions 2.1. Elements and atoms are described by Dalton’s atomic theory

  13. sulfur sulfur dioxide trioxide Mass S 32.06 g 32.06 g Mass O 32.00 g 48.00 g Use these data to prove the law of multiple proportions Using The Law Of Multiple Proportions 2.1. Elements and atoms are described by Dalton’s atomic theory

  14. Your Turn! Two substances are formed from A and B. AB and A2B3. If the mass ratio of A/B in AB is 3.49, what is the ratio of A/B in A2B3? • 0.431 • 3.49 • 0.286 • 2.33 • not enough information given 2.1. Elements and atoms are described by Dalton’s atomic theory

  15. Proof Of Atoms • Since the early 1980’s, the Scanning Tunneling Microscope (STM) has been used • A surface can be scanned for topographical information • The image for all matter shows spherical regions of matter-- atoms Atomically resolved STM image of clean Au(100). This image is made with an Omicron Low Temperature STM and RHK Technology electronics by Erwin Rossen, Eindhoven University of Technology, 2006. Parameters: p<1e-11 mbar, T=77 K, I_setpoint=6 nA, V_bias=1 mV, Au(100) surface is Ar sputtered (1,5 kV, 2uA, 30 minutes) and annealed (500°C, 30 minutes). 2.1. Elements and atoms are described by Dalton’s atomic theory

  16. Radioactivity • One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876-1934). • She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.

  17. Cathode Ray Tube (CRT) A gas filled glass tube that has electrical charge applied at both ends. Such a tube glows with light and is the precursor of the modern-day television screen. 2.2 Atoms are composed of subatomic particles

  18. Discovery Of The Electron By JJ Thomson • In 1897, Thomson placed a magnet near CRT and noted deflection of the beam • Repeated experiment with an electrical field and noted that the discharge was deflected by an electrical field toward the (+) plate • Announced discovery of (-) particle, later named “electron” by Stoney 2.2 Atoms are composed of subatomic particles

  19. Determining The Charge On An e-: Millikan 2.2 Atoms are composed of subatomic particles

  20. Rutherford’s Alpha Scattering Experiment Most alpha rays passed right through the Au A few were deflected off at an angle 1 in 8000 bounced back towards the alpha ray source 2.2 Atoms are composed of subatomic particles

  21. Since most of the alpha particles were not deflected, most of the atom is empty space. Since some of the particles were deflected, they encountered small particles of the same charge. Since some particles were reflected, there must be a small dense area. Rutherford’s Nuclear Model of the Atom 2.2 Atoms are composed of subatomic particles

  22. The modern view of the atom was developed by Ernest Rutherford(1871-1937). “It was about as credible as if you had fired a 15-inch artillery shell at a piece of paper and it came back and hit you” 02m11an1.mov

  23. Question:

  24. Discovery Of The Proton • Discovered in 1918 in Ernest Rutherford’s lab • Detected using a Mass Spectrometer 2.2 Atoms are composed of subatomic particles

  25. Discovery Of The Neutron • Chadwick determined that the nuclei of light atoms could be caused to disintegrate by being bombarded by alpha particles. • In collision of alpha particles with Be, a free neutron was created • the presence of the neutron confirmed in 1932 2.2 Atoms are composed of subatomic particles

  26. Subatomic Particles 2.2 Atoms are composed of subatomic particles

  27. Atomic Mass • Dalton’s atomic theory states that atoms of an element have a constant, characteristic atomic mass or atomic weightmeasured inamu (u) • Atomic masses are based on a standard mass, that of an atom of C • 1 atom of Carbon-12 = 12 u • Thus 1 u = 1/12 the mass of a Carbon-12 atom 2.2 Atoms are composed of subatomic particles

  28. Isotopes • Most elements in nature are uniform mixtures of two or more kinds of atoms with slightly different masses • Atoms of the same element with different masses are called isotopes • For example: there are 3 isotopes of hydrogen and 4 isotopes of iron • Chemically, isotopes have virtually identical properties 2.2 Atoms are composed of subatomic particles

  29. Atomic Notation • An element is a substance whose atoms all contain the identical number of protons, called the atomic number (Z) • Isotopes are distinguished by mass number(A): • Atomic number, Z = number of protons • Mass number, A = (number of protons) + (number of neutrons) • Note that for atoms, A is greater than Z: the symbol is top-heavy • For charge neutrality, the number of electrons and protons must be equal 2.2 Atoms are composed of subatomic particles

  30. 235 U 92 Mass number, A (protons + neutrons)  Chemical Symbol  Atomic number, Z (number of protons)  Example: uranium-235 This information can be summarized: • Number of protons = 92 ( = number of electrons) • Number of neutrons = 143 • Atomic number (Z) = 92 • Mass number (A) = 92 + 143 = 235 • Chemical symbol = U 2.2 Atoms are composed of subatomic particles

  31. Question: How many neutrons are there in an atom of sulfur-33? a: 16 b: 17 c: 33 d: 49

  32. Question: How many electrons are there in an atom of uranium-238? a: 92 b: 146 c: 238 d: 330

  33. Question:

  34. Learning Check: Fill in the blanks: symbol neutrons protons electrons 60Co 81Br 36 29 29 2.2 Atoms are composed of subatomic particles

  35. Your Turn! How many neutrons are there in 52Fe? • 52 • 55 • 26 • none of these 2.2 Atoms are composed of subatomic particles

  36. What is the total value of: • 3 quarters, two dimes and one nickel?

  37. Learning Check: Atomic Mass Naturally occurring chlorine is a mixture of two isotopes. In every sample of this element, 75.77% of the atoms are chlorine-35 and 24.23% are chlorine-37. The measured mass of chlorine-35 is 34.9689 u and that of chlorine-37 is 36.9659 u. Calculate the average atomic mass of chlorine. 2.2 Atoms are composed of subatomic particles

  38. Your Turn There are 2 isotopes of element Z. The first is 56.5% in abundance and has a mass of 152.3 u. If the atomic mass is 155.5 u, what is the mass of the other isotope? • 156 u • 44.5 u • 157. u • not enough information given • none of these 2.2 Atoms are composed of subatomic particles

  39. Question: Copper has two stable isotopes, copper-63 and copper-65. What is the abundance of copper-65? a: 5.75% b: 27.5% c: 50% d: 72.5% e: 95.5%

  40. Question:

  41. Problem Solving Calculate the average atomic mass of chromium of naturally occurring chromium based on the information given for its four isotopes: 4.31% 50Cr of mass 49.946 amu, 83.76% 52Cr of mass 51.941 amu, 9.55% 53Cr of mass 52.941 amu and 2.38% 54Cr of mass 53.939 amu.

  42. Problem Solving Naturally occurring Gallium consists of two isotopes. Calculate the percent abundances of Ga-69 and Ga-71 when the atomic mass is 69.72 amu and the isotopic masses are 68.926 and 70.925 amu respectively

  43. Periodic Table • arranged in numbered rows – “periods” • columns called “groups” or “families” 2.3. The periodic table is used to organize and correlate facts

  44. Periodic Table • Summarizes chemical and physical properties of the elements • Mendeleev first arranged atoms by increasing atomic mass. Noted repeating (periodic) properties • Modern table is arranged by increasing atomic number (Moseley) 2.3. The periodic table is used to organize and correlate facts

  45. Some Important Classifications: • A groups = representativeelementsor main group elements I A = alkali metals II A = alkaline earth metals VII A = halogens VIII = noble (also inert) gases • B groups = transition elements • Inner transition elements= elements 58 – 71 and 90 – 103 58 – 71 = lanthanide elements 90 – 103 = actinide elements 2.3. The periodic table is used to organize and correlate facts

  46. The modern periodic table 2.3. The periodic table is used to organize and correlate facts

  47. Metals, Nonmetals, And Metalloids 2.4. Elements can be metals, non-metals, or metalloids

  48. Your turn! Which of the following is correct? • Cu is a representative transition element • Na is an alkaline earth metal • Al is a semimetal in group IIIa • F is a representative halogen • None of these are correct 2.4. Elements can be metals, non-metals, or metalloids

  49. Properties Of Metals • reflect light (have metallic luster) • Can be hammered or rolled into thin sheets (are malleable) andcan be drawn into wire (are ductile) • Are solids at room temperature (except Hg) • conduct electricity and heat 2.4. Elements can be metals, non-metals, or metalloids

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