Atoms, Molecules, and Ions

Transcription

1 Chapter 2 Atoms, Molecules, l and Ions

2 Chapter 2 Table of Contents 2.1 The Early History of Chemistry 2.2 Fundamental Chemical Laws Dalton s Atomic Theory 2.4 Early Experiments to Characterize the Atom The Modern View of Atomic Structure: t An Introduction ti 2.6 Molecules and Ions An Introduction to the Periodic Table 2.8 Naming Simple Compounds Copyright Cengage Learning. All rights reserved 2

3 Section 2.1 The Early History of Chemistry 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. Copyright Cengage Learning. All rights reserved 3

4 Section 2.2 Fundamental Chemical Laws 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. Copyright Cengage Learning. All rights reserved 4

5 Section 2.2 Fundamental Chemical Laws 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. Copyright Cengage Learning. All rights reserved 5

6 Section 2.2 Fundamental Chemical Laws Law of Definite Composition The law of definite composition ( 일정성분비의법칙 ) states that Compounds always contain the same elements in a constant proportion by mass. Water is always 11.19% hydrogen and 88.81% oxygen by mass, no matter what its source. Ethanol is always 13.13% hydrogen, 52.14% carbon, and 34.73% oxygen by mass. Chapter 4 6

7 Section 2.2 Fundamental Chemical Laws Conservation of Mass Antoine Lavoisier found that the mass of substances before a chemical change was always equal to the mass of substances after a chemical change. This is the law of conservation of mass ( 질량보존의법칙 ). Matter is neither created nor destroyed in physical or chemical processes. Chapter 4 7

8 Section 2.3 Dalton s Atomic Theory Dalton s Theory A Summary of Dalton s Atomic Theory: 1. An element is composed of tiny, indivisible, indestructible particles called atoms. 2. All atoms of an element are identical and have the same properties. 3. Atoms of different elements combine to form compounds. 4. Compounds contain atoms in small whole number ratios. 5. Atoms can combine in more than one ratio to form different compounds. Chapter 5 8

9 Section 2.3 Dalton s Atomic Theory Dalton s Atomic Theory The first two parts of Dalton s theory were later proven incorrect. We will see this later. Proposals 3, 4, and 5 are still accepted today. Dalton s theory was an important step in the further development of atomic theory. Chapter 5 9

10 Section 2.4 Early Experiments to Characterize the Atom Subatomic Particles ( 아원자입자 ) About 50 years after Dalton s proposal, evidence was seen that atoms were divisible. Two subatomic particles were discovered. negatively charged electrons,, e positively charge protons, p + An electron has a relative charge of -1, and a proton has a relative charge of +1. Chapter 5 10

11 Section 2.4 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 particles that we now call electrons. Copyright Cengage Learning. All rights reserved 11

12 Section 2.4 Early Experiments to Characterize the Atom Cathode-Ray Tube Copyright Cengage Learning. All rights reserved 12

13 Section 2.4 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. Copyright Cengage Learning. All rights reserved 13

14 Section 2.4 Early Experiments to Characterize the Atom Rutherford s Gold Foil Experiment Copyright Cengage Learning. All rights reserved 14

15 Section 2.5 The Modern View of Atomic Structure: An Introduction The atom contains: Electrons found outside the nucleus; negatively charged. 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. Copyright Cengage Learning. All rights reserved 15

16 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. Copyright Cengage Learning. All rights reserved 16

17 Section 2.5 The Modern View of Atomic Structure: An Introduction Nuclear Atom Viewed in Cross Section Copyright Cengage Learning. All rights reserved 17

18 Section 2.5 The Modern View of Atomic Structure: An Introduction Subatomic Particles ( 아원자입자 ) 양성자 (Proton) + 중성자 (Neutron) + 전자 (Electron) 양성자 (Proton) : +1의전하량 - 양성자수가원소의종류와화학적성질을결정 - 양성자수 = 원자번호 (Z) - 질량 = 1.0 amu (1.67 x g) 중성자 (Neutron) : 0의전하량 - 같은원자라도중성자수가다를수있음 - 질량수 (mass number, A) = 양성자수 + 중성자수 - 질량 = 1.0 amu (1.67 x g) 전자 (Electron) : -1의전하량 - 중성원자에서양성자수와같음 ; 양성자수와차이가나면이온! - 원자의대부분공간차지 - 질량 = amu ( x g) Chapter 5 18

19 Section 2.5 The Modern View of Atomic Structure: An Introduction 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. Copyright Cengage Learning. All rights reserved 19

20 Section 2.5 The Modern View of Atomic Structure: An Introduction Isotopes 같은양성자의수 ; 다른중성자의수 같은화학적성질, 다른질량 원자번호가같기때문에동일한원소이다. Electron Proton Neutron carbon 12 carbon 13 carbon 14 stable stable unstable (radioactive) 질문 ) 238 X 라는원소는어느원소의동위원소인가? 92 a) Lead b) Calcium c) Uranium d) Niobium Chapter 5 20

21 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. Copyright Cengage Learning. All rights reserved 21

22 Section 2.6 Molecules and Ions Covalent Bonding Copyright Cengage Learning. All rights reserved 22

23 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). Copyright Cengage Learning. All rights reserved 23

24 Section 2.6 Molecules and Ions Molecular vs. Ionic Compounds Copyright Cengage Learning. All rights reserved 24

25 Section 2.7 An Introduction to the Periodic Table The Periodic Table Metals vs. Nonmetals Groups or Families elements in the same vertical columns; have similar chemical properties Periods horizontal rows of elements Copyright Cengage Learning. All rights reserved 25

26 Section 2.7 An Introduction to the Periodic Table Metals are on the left side of the periodic table, nonmetals are on the right side, and the semimetals are in between. 주기 (Period) 족 (Gr roup) Chapter 4 26

27 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 Copyright Cengage Learning. All rights reserved 27

28 Section 2.8 Naming Simple Compounds Naming Compounds Binary Compounds Composed of two elements Ionic and covalent compounds included Binary Ionic Compounds Metal nonmetal Binary Covalent Compounds Nonmetal nonmetal Copyright Cengage Learning. All rights reserved 28

29 Section 2.8 Naming Simple Compounds Binary Ionic Compounds (Type I) 1. The cation is always named first and the anion second. 2. A monatomic cation takes its name from the name of the parent element. 3. A monatomic anion is named by taking the root of the element name and adding ide. Copyright Cengage Learning. All rights reserved 29

30 Section 2.8 Naming Simple Compounds Binary Ionic Compounds (Type I) Examples: KCl Potassium chloride MgBr 2 Magnesium bromide CaO Calcium oxide Copyright Cengage Learning. All rights reserved 30

31 Section 2.8 Naming Simple Compounds 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. Copyright Cengage Learning. All rights reserved 31

32 Section 2.8 Naming Simple Compounds Binary Ionic Compounds (Type II) Examples: CuBr Copper(I) bromide FeS Iron(II) sulfide PbO 2 Lead(IV) oxide Copyright Cengage Learning. All rights reserved 32

33 Section 2.8 Naming Simple Compounds Polyatomic Ions Must be memorized (see Table 2.5 on pg. 62 in text). Examples of compounds containing polyatomic ions: NaOH Sodium hydroxide Mg(NO 3 ) 2 Magnesium nitrate (NH 4 ) 2 SO 4 Ammonium sulfate Copyright Cengage Learning. All rights reserved 33

34 Section 2.8 Naming Simple Compounds Formation of Ionic Compounds Copyright Cengage Learning. All rights reserved 34

35 Section 2.8 Naming Simple Compounds Binary Covalent Compounds (Type III) Formed between two nonmetals. 1. The first element in the formula is named first, using the full element name. 2. The second element is named as if it were an anion. 3. Prefixes are used to denote the numbers of atoms present. 4. The prefix mono- is never used for naming the first element. Copyright Cengage Learning. All rights reserved 35

36 Section 2.8 Naming Simple Compounds Prefixes Used to Indicate Number in Chemical Names Copyright Cengage Learning. All rights reserved 36

37 Section 2.8 Naming Simple Compounds Binary Covalent Compounds (Type III) Examples: CO 2 Carbon dioxide SF 6 Sulfur hexafluoride N 2 O 4 Dinitrogen tetroxide Copyright Cengage Learning. All rights reserved 37

38 Section 2.8 Naming Simple Compounds Overall Strategy for Naming Chemical Compounds Copyright Cengage Learning. All rights reserved 38

39 Section 2.8 Naming Simple Compounds Flowchart for Naming Binary Compounds Copyright Cengage Learning. All rights reserved 39

40 Section 2.8 Naming Simple Compounds 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. Copyright Cengage Learning. All rights reserved 40

41 Section 2.8 Naming Simple Compounds 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 H 2 S Hydrosulfuric acid Copyright Cengage Learning. All rights reserved 41

42 Section 2.8 Naming Simple Compounds 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 Copyright Cengage Learning. All rights reserved 42

43 Section 2.8 Naming Simple Compounds 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 Copyright Cengage Learning. All rights reserved 43

44 Section 2.8 Naming Simple Compounds Flowchart for Naming Acids Copyright Cengage Learning. All rights reserved 44