Chapter 2 Atoms, Molecules, and Ions

Chapter 2 Table of Contents Return to TOC Copyright © Cengage Learning. All rights reserved The Early History of Chemistry 2.2 Fundamental Chemical Laws 2.3 Dalton’s Atomic Theory 2.4 Early Experiments to Characterize the Atom 2.5 The Modern View of Atomic Structure: An Introduction 2.6Molecules and Ions 2.7An Introduction to the Periodic Table

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 3 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

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 4 All of the materials in the universe can be chemically broken down into about 100 different elements. WordsCompounds Compounds are made by combining atoms of the elements just as words are constructed from the letters in the alphabet. The Elements

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 5 Greek Thinking circa 400 B.C. Empedocles ( ) All things made up of 4 elements Fire Earth Water Air Democritus ( ) Was the first to propose the atom

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 6 The Atom: Shelved for 2,000 Years 400 B.C. ~ 1600 A.D. (Alchemist Period) Robert Boyle ( ) 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.

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 Return to TOC Copyright © Cengage Learning. All rights reserved 8 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. –Sometimes the symbol is taken from the element’s original Latin or Greek name. Examples: Oxygen O Krypton Kr Examples: gold Au aurum lead Pb plumbum BromineBr“stench” in Greek Chuck Norris element, Deceased Chemist

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 9 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

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 10 Formula Examples H 2 OWater SO 3 Acid rain C 6 H 12 O 6 Glucose Fe 2 (CO 3 ) 3 How many of each atom type in the following formulas? P 4 O 10 UF 6 AlCl 3 (NH 4 ) 2 C 8 H 4 O 2 Al 2 (Cr 2 O 7 ) Al(NO 3 ) 3

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 11 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…

Section 2.1 The Early History of Chemistry Return to TOC Copyright © Cengage Learning. All rights reserved 12 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

Section 2.2 Fundamental Chemical Laws Return to TOC Copyright © Cengage Learning. All rights reserved 13 Objectives 2.2 – 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

Section 2.2 Fundamental Chemical Laws Return to TOC Copyright © Cengage Learning. All rights reserved 14 John Dalton English Schoolteacher ( ) 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.

Section 2.3 Dalton’s Atomic Theory Return to TOC Copyright © Cengage Learning. All rights reserved 15 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. Dalton’s Atomic Theory (1808)

Section 2.3 Dalton’s Atomic Theory Return to TOC Copyright © Cengage Learning. All rights reserved 16 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. Dalton’s Atomic Theory (continued)

Section 2.3 Dalton’s Atomic Theory Return to TOC Copyright © Cengage Learning. All rights reserved 17 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.

Section 2.3 Dalton’s Atomic Theory Return to TOC Copyright © Cengage Learning. All rights reserved 18 Law of conservation of mass (Lavoisier):  Mass is neither created nor destroyed. Law of definite proportion (Proust):  A given compound always contains exactly the same proportion of elements by mass. CO 2 is always CO 2 ! 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. C 2 O 4 = CO 2 Three Important Laws

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 19 The Structure of the Atom Experiments by J.J. Thomson showed that atoms contain electrons. Cathode ray tube Video Clip & CRT Monitor Rigby, ID

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 20 The Structure of the Atom The Plum Pudding Model (Tapioca) JJ Thompson ( ) Nobel Prize in Physics 1908 Intellectual discovery of the + particle to keep neutrality

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 21 Performed experiments involving charged oil drops. Determined the magnitude of the charge on a single electron. Calculated the mass of the electron. Robert Millikan (1909)

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 22 Millikan Oil Drop Experiment

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 23 Ernest Rutherford New Zealand 1908 Nobel Prize in Chemistry

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 24 The Structure of the Atom Rutherford’s Experiment Student of Thomson

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 25 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 (b) Actual results

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 26 Rutherford’s Gold Foil Experiment pHetpHet

Section 2.4 Early Experiments to Characterize the Atom Return to TOC Copyright © Cengage Learning. All rights reserved 27 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.

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 28 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...

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 29 The nucleus is:  Small compared with the overall size of the atom.  Extremely dense; accounts for almost all of the atom’s mass.

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 30 Isotopes Isotopes are atoms with the same number of protons but different numbers of neutrons. Remember the bean!

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 31 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 TopesQuerque Topes

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 32 Examples Carbon CCarbon CCarbon C # proton # neutron # electron The number of protons DEFINES the atom type.

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 33 Practice – List the number of Protons, Neutrons, and Electrons in each neutral species Sr Hg Magnesium-24 Silver with 61 neutrons Phosphorus with 17 neutrons Ag-108 What did the chemist say when she found two isotopes of Helium?

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 34 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

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 Return to TOC Copyright © Cengage Learning. All rights reserved 36 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.

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 37 Nonmetals tend to gain one or more electrons to form negative ions called anions. Ions Anions are named by using the root of the atom name followed by the suffix –ide.

Section 2.5 The Modern View of Atomic Structure: An Introduction Return to TOC Copyright © Cengage Learning. All rights reserved 38 Objectives Review 2.2 – 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 8.Work Session: pg 68 #2,4,5 pg # 5,9,17,18,19,21, 22 skip b, 39,51,49,73 Challenge! (Hint Na makes -1 charge)

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 39 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

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 40 The periodic table is organized to group elements with similar properties in vertical columns. (Families)

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 41 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.

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 42 Physical Properties of Metals 1.Efficient conduction of heat and electricity 2.Malleability (can be hammered into thin sheets) 3.Ductility (can be pulled into wires) 4.A lustrous (shiny) appearance

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 43 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…)

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 44 Natural States of the Elements Diatomic Molecules Nitrogen gas contains N 2 molecules. Oxygen gas contains O 2 molecules.

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 45 Natural States of the Elements Diatomic Molecules (The Diatomic 7 Yeehaw!)

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 46 Natural States of the Elements Elemental Solids (Allotrope same element different form) DiamondGraphiteBuckminsterfullerene Carbon atoms

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 47 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

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 48 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. -Einstein-

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 49 This is the end of the required material………….

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 50 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. Acids

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 51 If the anion does not contain oxygen, the acid is named with the prefix hydro– and the suffix –ic. Examples: HClHydrochloric acid HCNHydrocyanic acid H 2 SHydrosulfuric acid Acids

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 52 If the anion does contain oxygen:  The suffix –ic is added to the root name if the anion name ends in –ate. Examples: HNO 3 Nitric acid H 2 SO 4 Sulfuric acid HC 2 H 3 O 2 Acetic acid Acids

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 53 If the anion does contain oxygen:  The suffix –ous is added to the root name if the anion name ends in –ite. Examples: HNO 2 Nitrous acid H 2 SO 3 Sulfurous acid HClO 2 Chlorous acid Acids

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 54 Flowchart for Naming Acids

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 55 Covalent Bonds  Bonds form between atoms by sharing electrons.  Resulting collection of atoms is called a molecule. Chemical Bonds

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 56 Covalent Bonding

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 57 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). Chemical Bonds

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 58 Molecular vs. Ionic Compounds

Section 2.6 Molecules and Ions Return to TOC Copyright © Cengage Learning. All rights reserved 59 Exercise A certain isotope X + contains 54 electrons and 78 neutrons. What is the mass number of this isotope? 133

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 60 The Periodic Table

Section 2.7 An Introduction to the Periodic Table Return to TOC Copyright © Cengage Learning. All rights reserved 61 Table of common charges formed when creating ionic compounds. Groups or Families Group or FamilyCharge Alkali Metals (1A)1+ Alkaline Earth Metals (2A) 2+ Halogens (7A)1– Noble Gases (8A)0