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Chapter 2 Atoms, Molecules, and Ions Chapter 2 Table of Contents 2.1 2.2 2.3 2.4 2.5 2.6 2.7 The Early History of Chemistry Fundamental Chemical Laws Dalton’s Atomic Theory Early Experiments to Characterize the Atom The Modern View of Atomic Structure: An Introduction Molecules and Ions An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 2 Section 2.1 The Early History of Chemistry Objectives 1. To learn about the relative abundances of the elements 2. To learn about early Greek thinking 3. To learn the names and symbols of some elements 4. To learn how a formula describes a compound’s composition Return to TOC Copyright © Cengage Learning. All rights reserved 3 Section 2.1 The Early History of Chemistry The Elements • All of the materials in the universe can be chemically broken down into about 100 different elements. • Compounds are made by combining atoms of the elements just as words are constructed from the letters in the alphabet. Words Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 4 Section 2.1 The Early History of Chemistry Greek Thinking circa 400 B.C. • Empedocles (492-432 ) • • • • • • • All things made up of 4 elements Fire Earth Water Air Democritus (460 -370) Was the first to propose the atom Return to TOC Copyright © Cengage Learning. All rights reserved 5 Section 2.1 The Early History of Chemistry The Atom: Shelved for 2,000 Years • 400 B.C. ~ 1600 A.D. (Alchemist Period) • Robert Boyle (1627-1691) defined an element as something that could not be broken down into simpler substances. He was one of the first to bring experimentation and repetition thereby bringing an end to the Greek view of the 4 elements. Return to TOC Copyright © Cengage Learning. All rights reserved 6 Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 7 Section 2.1 The Early History of Chemistry Names and Symbols for the Elements • Each element has a name and a symbol. – The symbol usually consists of the first one or two letters of the element’s name. • Examples: Oxygen Krypton O Kr – Sometimes the symbol is taken from the element’s original Latin or Greek name. • Examples: gold lead Au Pb aurum plumbum Bromine Br “stench” in Greek Chuck Norris element, Deceased Chemist Copyright © Cengage Learning. All rights reserved Return to TOC 8 Section 2.1 The Early History of Chemistry Formulas of Compounds • A compound is represented by a chemical formula in which the number and kind of atoms present is shown by using the element symbols and subscripts. Example: the simple sugar, glucose Return to TOC Copyright © Cengage Learning. All rights reserved 9 Section 2.1 The Early History of Chemistry Formula Examples • • • • • • • • • • • H2O Water SO3 Acid rain C6H12O6 Glucose Fe2(CO3)3 How many of each atom type in the following formulas? P4O10 UF6 AlCl3 (NH4)2C8H4O2 Al2(Cr2O7) Al(NO3)3 Copyright © Cengage Learning. All rights reserved Return to TOC 10 Section 2.1 The Early History of Chemistry Periodic Table Name Game • Someone starts by naming an element. • They then call on another player who must name an element that starts with the last letter of the previous element name. • They then call on the next player and on and on… Return to TOC Copyright © Cengage Learning. All rights reserved 11 Section 2.1 The Early History of Chemistry Objectives Review 1. To learn about the relative abundances of the elements 2. To learn about early Greek thinking 3. To learn the names and symbols of some elements 4. To learn how a formula describes a compound’s composition 5. Work Session: pg 71 # 35,37 Return to TOC Copyright © Cengage Learning. All rights reserved 12 Section 2.2 Fundamental Chemical Laws Objectives 2.2 – 2.6 1. To learn about Dalton’s Theory of Atoms 2. To understand and illustrate three important Laws of Chemistry 3. To understand Thomson’s, Millikan’s, and Rutherford’s work 4. To understand the modern view of the atom 5. To learn about the terms isotope, atomic number, and mass number 6. To understand the use of the symbol to describe a given atom 7. To describe the formation of ions from their parent atoms Return to TOC Copyright © Cengage Learning. All rights reserved 13 Section 2.2 • • • • • Fundamental Chemical Laws John Dalton English Schoolteacher (1766-1844) 100 years after Boyle Dalton started his own school at the age of 12! At age 15, went into business with uncle because he was threatened by his older students when he tried to discipline them! Chemical analysis and synthesis can go no further than to the separation of particles from one another, and to their reunion. No new creation or destruction of matter is within reach of chemical agency. We might as well try to introduce a new planet into the solar system and to annihilate one already in existence, as to create or destroy a particle of hydrogen- J.D. Return to TOC Copyright © Cengage Learning. All rights reserved 14 Section 2.3 Dalton’s Atomic Theory Dalton’s Atomic Theory (1808) • • • Each element is made up of tiny particles called atoms. The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways. Chemical compounds are formed when atoms of different elements combine with each other. A given compound always has the same relative numbers and types of atoms. Return to TOC Copyright © Cengage Learning. All rights reserved 15 Section 2.3 Dalton’s Atomic Theory Dalton’s Atomic Theory (continued) • • Chemical reactions involve reorganization of the atoms—changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction. Return to TOC Copyright © Cengage Learning. All rights reserved 16 Section 2.3 Dalton’s Atomic Theory Concept Check Which of the following statements regarding Dalton’s atomic theory are still consistent with modern atomic theory? I. Elements are made of tiny particles called atoms. II. All atoms of a given element are identical. III. A given compound always has the same relative numbers and types of atoms. IV. Atoms are indestructible. Return to TOC Copyright © Cengage Learning. All rights reserved 17 Section 2.3 Dalton’s Atomic Theory Three Important Laws • Law of conservation of mass (Lavoisier): • Law of definite proportion (Proust): • Mass is neither created nor destroyed. A given compound always contains exactly the same proportion of elements by mass. CO2 is always CO2! Law of multiple proportions (Dalton): When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers. C2O4 = CO2 Return to TOC Copyright © Cengage Learning. All rights reserved 18 Section 2.4 Early Experiments to Characterize the Atom The Structure of the Atom • Experiments by J.J. Thomson showed that atoms contain electrons. • Cathode ray tube • Video Clip & CRT Monitor Rigby, ID 1 2 3 Return to TOC Copyright © Cengage Learning. All rights reserved 19 Section 2.4 Early Experiments to Characterize the Atom The Structure of the Atom The Plum Pudding Model (Tapioca) JJ Thompson (1856-1940) Nobel Prize in Physics 1908 Intellectual discovery of the + particle to keep neutrality Copyright © Cengage Learning. All rights reserved Return to TOC 20 Section 2.4 Early Experiments to Characterize the Atom Robert Millikan (1909) • • • Performed experiments involving charged oil drops. Determined the magnitude of the charge on a single electron. Calculated the mass of the electron. Return to TOC Copyright © Cengage Learning. All rights reserved 21 Section 2.4 Early Experiments to Characterize the Atom Millikan Oil Drop Experiment Return to TOC Copyright © Cengage Learning. All rights reserved 22 Section 2.4 Early Experiments to Characterize the Atom Ernest Rutherford • 1871-1937 • New Zealand • 1908 Nobel Prize in Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 23 Section 2.4 Early Experiments to Characterize the Atom The Structure of the Atom Rutherford’s Experiment Student of Thomson Return to TOC Copyright © Cengage Learning. All rights reserved 24 Section 2.4 Early Experiments to Characterize the Atom The Structure of the Atom • Results of the Rutherford experiment (a) The results that the metal foil experiment would have yielded if the plum pudding model had been correct Copyright © Cengage Learning. All rights reserved (b) Actual results Return to TOC 25 Section 2.4 Early Experiments to Characterize the Atom Rutherford’s Gold Foil Experiment pHet Return to TOC Copyright © Cengage Learning. All rights reserved 26 Section 2.4 Early Experiments to Characterize the Atom Introduction to the Modern Concept of Atomic Structure • Ernest Rutherford showed that atoms have internal structure. – The nucleus, which is at the center of the atom, contains protons (positively charged) and neutrons (uncharged 1932). – Neutrons were another intellectual discovery for reasons of mass and repulsive space between the protons – Electrons move around the nucleus. Copyright © Cengage Learning. All rights reserved Return to TOC 27 Section 2.5 The Modern View of Atomic Structure: An Introduction Introduction to the Modern Concept of Atomic Structure Comparing the Parts of an Atom If a grape is a nucleus, the nearest electron is 1 mile away! Neutron went to dinner... Return to TOC Copyright © Cengage Learning. All rights reserved 28 Section 2.5 The Modern View of Atomic Structure: An Introduction • The nucleus is: Small compared with the overall size of the atom. Extremely dense; accounts for almost all of the atom’s mass. Return to TOC Copyright © Cengage Learning. All rights reserved 29 Section 2.5 The Modern View of Atomic Structure: An Introduction Isotopes • Isotopes are atoms with the same number of protons but different numbers of neutrons. Remember the bean! Copyright © Cengage Learning. All rights reserved Return to TOC 30 Section 2.5 The Modern View of Atomic Structure: An Introduction Isotopes • Show almost identical chemical properties; chemistry of atom is due to its electrons. • In nature most elements contain mixtures of isotopes. • A particular isotope is represented by the symbol . The Simpson’s Baseball.. Querque Topes Return to TOC Copyright © Cengage Learning. All rights reserved 31 Section 2.5 The Modern View of Atomic Structure: An Introduction Examples Carbon-12 • # proton 12 6C Carbon-13 136C Carbon-14 146C • # neutron • # electron • The number of protons DEFINES the atom type. Return to TOC Copyright © Cengage Learning. All rights reserved 32 Section 2.5 The Modern View of Atomic Structure: An Introduction Practice – List the number of Protons, Neutrons, and Electrons in each neutral species • • • • • • • 90 38Sr 201 Hg 80 Magnesium-24 Silver with 61 neutrons Phosphorus with 17 neutrons Ag-108 What did the chemist say when she found two isotopes of Helium? Return to TOC Copyright © Cengage Learning. All rights reserved 33 Section 2.5 The Modern View of Atomic Structure: An Introduction Exercise A certain isotope X contains 23 protons and 28 neutrons. • What is the mass number of this isotope? • Identify the element. Mass Number = 51 Vanadium Return to TOC Copyright © Cengage Learning. All rights reserved 34 Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 35 Section 2.6 Molecules and Ions Ions • Atoms can form ions by gaining or losing electrons. – Metals tend to lose one or more electrons to form positive ions called cations. – Cations are generally named by using the name of the parent atom. Copyright © Cengage Learning. All rights reserved Return to TOC 36 Section 2.6 Molecules and Ions Ions • Nonmetals tend to gain one or more electrons to form negative ions called anions. • Anions are named by using the root of the atom name followed by the suffix –ide. Return to TOC Copyright © Cengage Learning. All rights reserved 37 Section 2.5 The Modern View of Atomic Structure: An Introduction Objectives Review 2.2 – 2.6 1. 2. 3. 4. 5. 6. 7. 8. To learn about Dalton’s Theory of Atoms To understand and illustrate three important Laws of Chemistry To understand Thomson’s, Millikan’s, and Rutherford’s work To understand the modern view of the atom To learn about the terms isotope, atomic number, and mass number To understand the use of the symbol to describe a given atom To describe the formation of ions from their parent atoms Work Session: pg 68 #2,4,5 pg 69-73 # 5,9,17,18,19,21, 22 skip b, 39,51,49,73 Challenge! (Hint Na makes -1 charge) Return to TOC Copyright © Cengage Learning. All rights reserved 38 Section 2.7 An Introduction to the Periodic Table Objectives 1. To learn the various features of the periodic table 2. To learn some of the properties of metals, nonmetals and metalloids 3. To learn the natures of the common elements Return to TOC Copyright © Cengage Learning. All rights reserved 39 Section 2.7 An Introduction to the Periodic Table • The periodic table is organized to group elements with similar properties in vertical columns. (Families) Return to TOC Copyright © Cengage Learning. All rights reserved 40 Section 2.7 An Introduction to the Periodic Table • Most elements are metals and occur on the left side. • The nonmetals appear on the right side. • Metalloids are elements that have some metallic and some nonmetallic properties. Return to TOC Copyright © Cengage Learning. All rights reserved 41 Section 2.7 An Introduction to the Periodic Table • Physical Properties of Metals 1. 2. 3. 4. Efficient conduction of heat and electricity Malleability (can be hammered into thin sheets) Ductility (can be pulled into wires) A lustrous (shiny) appearance Return to TOC Copyright © Cengage Learning. All rights reserved 42 Section 2.7 An Introduction to the Periodic Table Natural States of the Elements • Most elements are very reactive. • Elements are not generally found in uncombined form. – Exceptions are: • Noble metals – gold, platinum and silver • Noble gases – Group 8 (Bumped the Table…) Return to TOC Copyright © Cengage Learning. All rights reserved 43 Section 2.7 An Introduction to the Periodic Table Natural States of the Elements • Diatomic Molecules Nitrogen gas contains N2 molecules. Oxygen gas contains O2 molecules. Return to TOC Copyright © Cengage Learning. All rights reserved 44 Section 2.7 An Introduction to the Periodic Table Natural States of the Elements • Diatomic Molecules (The Diatomic 7 Yeehaw!) Return to TOC Copyright © Cengage Learning. All rights reserved 45 Section 2.7 An Introduction to the Periodic Table Natural States of the Elements • Elemental Solids (Allotrope same element different form) Carbon atoms Diamond Graphite Buckminsterfullerene Return to TOC Copyright © Cengage Learning. All rights reserved 46 Section 2.7 An Introduction to the Periodic Table Objectives Review 1. To learn the various features of the periodic table 2. To learn some of the properties of metals, nonmetals and metalloids 3. To learn the natures of the common elements 4. QUOTE NEXT SLIDE Return to TOC Copyright © Cengage Learning. All rights reserved 47 Section 2.7 An Introduction to the Periodic Table Food For Thought • The only objective reality in the universe is that which constitutes a combination of every point of experience. • Absolute truth can be ascertained only through the sum total of all relative observations. -EinsteinReturn to TOC Copyright © Cengage Learning. All rights reserved 48 Section 2.7 An Introduction to the Periodic Table This is the end of the required material…………. Return to TOC Copyright © Cengage Learning. All rights reserved 49 Section 2.7 An Introduction to the Periodic Table Acids • • Acids can be recognized by the hydrogen that appears first in the formula—HCl. Molecule with one or more H+ ions attached to an anion. Return to TOC Copyright © Cengage Learning. All rights reserved 50 Section 2.7 An Introduction to the Periodic Table Acids • • If the anion does not contain oxygen, the acid is named with the prefix hydro– and the suffix –ic. Examples: HCl Hydrochloric acid HCN Hydrocyanic acid H2S Hydrosulfuric acid Return to TOC Copyright © Cengage Learning. All rights reserved 51 Section 2.7 An Introduction to the Periodic Table Acids • If the anion does contain oxygen: The suffix –ic is added to the root name if the anion name ends in –ate. • Examples: HNO3 Nitric acid H2SO4 Sulfuric acid HC2H3O2 Acetic acid Return to TOC Copyright © Cengage Learning. All rights reserved 52 Section 2.7 An Introduction to the Periodic Table Acids • If the anion does contain oxygen: The suffix –ous is added to the root name if the anion name ends in –ite. • Examples: HNO2 Nitrous acid H2SO3 Sulfurous acid HClO2 Chlorous acid Return to TOC Copyright © Cengage Learning. All rights reserved 53 Section 2.7 An Introduction to the Periodic Table Flowchart for Naming Acids Return to TOC Copyright © Cengage Learning. All rights reserved 54 Section 2.6 Molecules and Ions Chemical Bonds • Covalent Bonds Bonds form between atoms by sharing electrons. Resulting collection of atoms is called a molecule. Return to TOC Copyright © Cengage Learning. All rights reserved 55 Section 2.6 Molecules and Ions Covalent Bonding Return to TOC Copyright © Cengage Learning. All rights reserved 56 Section 2.6 Molecules and Ions Chemical Bonds • Ionic Bonds Bonds form due to force of attraction between oppositely charged ions. Ion – atom or group of atoms that has a net positive or negative charge. Cation – positive ion; lost electron(s). Anion – negative ion; gained electron(s). Return to TOC Copyright © Cengage Learning. All rights reserved 57 Section 2.6 Molecules and Ions Molecular vs. Ionic Compounds Return to TOC Copyright © Cengage Learning. All rights reserved 58 Section 2.6 Molecules and Ions Exercise A certain isotope X+ contains 54 electrons and 78 neutrons. • What is the mass number of this isotope? 133 Return to TOC Copyright © Cengage Learning. All rights reserved 59 Section 2.7 An Introduction to the Periodic Table The Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 60 Section 2.7 An Introduction to the Periodic Table Groups or Families • Table of common charges formed when creating ionic compounds. Group or Family Charge Alkali Metals (1A) 1+ Alkaline Earth Metals (2A) 2+ Halogens (7A) 1– Noble Gases (8A) 0 Return to TOC Copyright © Cengage Learning. All rights reserved 61