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Chapter Two: ATOMS, MOLECULES, AND IONS. Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 2 Early History of Chemistry Greeks.

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Presentation on theme: "Chapter Two: ATOMS, MOLECULES, AND IONS. Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 2 Early History of Chemistry Greeks."— Presentation transcript:

1 Chapter Two: ATOMS, MOLECULES, AND IONS

2 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 2 Early History of Chemistry Greeks were the first to attempt to explain why chemical changes occur. Alchemy dominated for 2000 years: –Several elements discovered –Mineral acids prepared Robert Boyle was the first “chemist”: –Performed quantitative experiments 2.1

3 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 3 Three Important Laws 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 2.2

4 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 4 Three Important Laws (continued) 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 2.2

5 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 5 Dalton’s Atomic Theory (1808) Each element is made up of tiny particles called atoms. 2.3

6 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 6 Dalton’s Atomic Theory (continued) The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways. 2.3

7 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 7 Dalton’s Atomic Theory (continued) 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. 2.3

8 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 8 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. 2.3

9 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 9 Concept Check Which of the following statements regarding Dalton’s atomic theory are still believed to be true? 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.

10 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 10 Avogadro’s Hypothesis (1811) At the same temperature and pressure, equal volumes of different gases contain the same number of particles: –5 liters of oxygen –5 liters of nitrogen –Same number of particles! 2.3

11 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 11 Gay-Lussac and Avogadro Gay-Lussac measured (under same conditions of T and P) the volumes of gases that reacted with each other. Avogadro’s Hypothesis: –At the same T and P, equal volumes of different gases contain the same number of particles 2.3

12 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 12 Representing Gay-Lussac’s Results 2.3

13 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 13 Representing Gay-Lussac’s Results 2.3

14 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 14 Representing Gay-Lussac’s Results 2.3

15 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 15 Representing Gay-Lussac’s Results 2.3

16 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 16 Early Experiments to Characterize the Atom J. J. Thomson ( ): –Postulated the existence of electrons using cathode-ray tubes –Determined the charge-to-mass ratio of an electron –The atom must also contain positive particles that balance exactly the negative charge carried by the electrons 2.4

17 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 17 Cathode Ray Tube 2.4

18 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 18 Early Experiments to Characterize the Atom Robert Millikan (1909): –Performed experiments involving charged oil drops –Determined the magnitude of the electron charge –Calculated the mass of the electron 2.4

19 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 19 Millikan Oil Drop Experiment 2.4

20 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 20 Early Experiments to Characterize the Atom Ernest Rutherford (1911): –Explained the nuclear atom –Atom has a dense center of positive charge called the nucleus –Electrons travel around the nucleus at a relatively large distance 2.4

21 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 21 Rutherford’s Gold Foil Experiment 2.4

22 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 22 The Modern View of Atomic Structure The atom contains:  Electrons  Protons – found in the nucleus; positive charge equal in magnitude to the electron’s negative charge  Neutrons – found in the nucleus; no charge; virtually same mass as a proton 2.5

23 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 23 The Modern View of Atomic Structure The nucleus is: –Small compared with the overall size of the atom –Extremely dense; accounts for almost all of the atom’s mass 2.5

24 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 24 Nuclear Atom Viewed in Cross Section

25 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 25 The Modern View of Atomic Structure Isotopes: –Atoms with the same number of protons but different numbers of neutrons –Show almost identical chemical properties; chemistry of atom is due to its electrons –In nature most elements contain mixtures of isotopes 2.5

26 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 26 Two Isotopes of Sodium 2.5

27 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 27 Exercise A certain isotope X + contains 54 electrons and 78 neutrons. What is the mass number of this isotope? 2.5/2.6

28 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 28 Chemical Bonds Covalent Bonds: –Bonds form between atoms by sharing electrons –Resulting collection of atoms is called a molecule 2.6

29 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 29 Covalent Bonding 2.6

30 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 30 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) 2.6

31 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 31 Molecular vs. Ionic Compounds 2.6

32 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 32 The Periodic Table Metals vs. Nonmetals Groups or Families – elements in the same vertical columns –Alkali metals, alkaline earth metals, halogens, and noble gases Periods – horizontal rows of elements 2.7

33 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 33 The Periodic Table 2.7

34 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 34 Naming Compounds Binary Compounds: –Composed of two elements –Ionic and covalent compounds included Binary Ionic Compounds: –Metal-nonmetal Binary Covalent Compounds: –Nonmetal to nonmetal 2.8

35 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 35 Binary Ionic Compounds (Type I) Cation is always named first and the anion second. Monatomic cation has the same name as its parent element. Monatomic anion is named by taking the root of the element name and adding –ide. 2.8

36 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 36 Binary Ionic Compounds (Type I) Examples: KClPotassium chloride MgBr 2 Magnesium bromide CaOCalcium oxide 2.8

37 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 37 Binary Ionic Compounds (Type II) Metals in these compounds form more than one type of positive charge. Charge on the metal ion must be specified. Roman numeral indicates the charge of the metal cation. Transition metal cations usually require a Roman numeral. 2.8

38 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 38 Binary Ionic Compounds (Type II) Examples: CuBrCopper(I) bromide FeSIron(II) sulfide PbO 2 Lead(IV) oxide 2.8

39 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 39 Polyatomic Ions Must be memorized (see Table 2.5 on pg. 62 in text). Examples of compounds containing polyatomic ions: NaOHSodium hydroxide Mg(NO 3 ) 2 Magnesium nitrate (NH 4 ) 2 SO 4 Ammonium sulfate 2.8

40 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 40 Formation of Ionic Compounds 2.8

41 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 41 Binary Covalent Compounds (Type III) Formed between two nonmetals. First element is named first, using the full element name. Second element is named as if it were an anion. Prefixes are used to denote the numbers of atoms present. Prefix mono- is never used for naming the first element. 2.8

42 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 42 Binary Covalent Compounds (Type III) Examples: CO 2 Carbon dioxide SF 6 Sulfur hexafluoride N 2 O 4 Dinitrogen tetroxide 2.8

43 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 43 Overall Strategy for Naming Chemical Compounds

44 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 44 Flowchart for Naming Binary Compounds

45 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 45 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. 2.8

46 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 46 Acids 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 2.8

47 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 47 Acids 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 2.8

48 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 48 Acids 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 2.8

49 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 49 Flowchart for Naming Acids

50 Copyright © Houghton Mifflin Company. All rights reserved. Chapter 2 | Slide 50 Exercise Which of the following compounds is named incorrectly? a) KNO 3 potassium nitrate b) TiO 2 titanium(II) peroxide c) Sn(OH) 4 tin(IV) hydroxide d) PBr 5 phosphorus pentabromide e) CaCrO 4 calcium chromate 2.8


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