1. Chapter 4Atoms and Elements Elements and Symbols The Periodic Table The Atom Atomic and Mass Numbers Isotopes and Atomic Mass Electron Energy Levels You will need your textbook or copy of a periodic table for class !!!!!!!!!!

2. Chapter 4 – Slide 2 of 67 Pure Substances Elements Compounds

3. Chapter 4 – Slide 3 of 67 Elements are Pure substances that cannot be separated into simpler substances by ordinary laboratory processes. The building blocks of matter. gold carbon aluminum Elements Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

4. Chapter 4 – Slide 4 of 67 Sources of Some Element Names Some elements are named for planets, mythological figures, minerals, colors, scientists, and places.

5. Chapter 4 – Slide 5 of 67 Historical Perspective

6. Chapter 4 – Slide 6 of 67 A symbol Represents the name of an element. Consists of 1 or 2 letters. Starts with a capital letter. Examples: 1-Letter Symbols 2-Letter Symbols C carbon Co cobalt N nitrogenCa calcium F fluorine Al aluminum O oxygen Mg magnesium Symbols of Elements

7. Chapter 4 – Slide 7 of 67 Several symbols are derived from Latin names as shown below: Cu, copper (cuprum)Au, gold (aurum) Fe, iron (ferrum) Ag, silver (argentum ) Symbols from Latin Names

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9. Chapter 4 – Slide 9 of 67 A pure substance is classified as An element when composed of one type of atom. A compound when composed of two or more different elements combined in a definite ratio. Pure Substances

10. Chapter 4 – Slide 10 of 67 Elements v. Compounds v. Mixtures: Review Recall definition of compound. –A compound is when two or more different elements combine in a definite ratio. NaCl MgCl 2 AlCl 3 Molecular element is when both of the atoms in the molecule are the same element. H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2

11. Chapter 4 – Slide 11 of 67 A closer look at the Periodic Table

12. Chapter 4 – Slide 12 of 67 Modern Periodic Table Mendeleev – Father of the Periodic Table Periodic Law of the Elements – when elements are arranged in a particular order (increasing atomic number), elements of similar properties occur at periodic intervals Arranged into: –Groups/families – vertical columns –Periods – horizontal rows http://www.woodrow.org/teachers/chemistry/institutes/1992/MENDELEEV.GIF

13. Chapter 4 – Slide 13 of 67 Arrangement of the Periodic Table The blocks of the periodic table:

14. Chapter 4 – Slide 14 of 67 The Periodic Table – All Stretched Out

15. Chapter 4 – Slide 15 of 67 Groups and Periods On the periodic table Elements are arranged according to similar properties. Groups contain elements with similar properties in vertical columns. Periods are horizontal rows of elements.

16. Chapter 4 – Slide 16 of 67 Groups and Periods (Rows) Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

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18. Chapter 4 – Slide 18 of 67 Group Numbers Use the letter A for the representative elements 1A to 8A and the letter B for the transition elements. Also use numbers 1-18 for the columns from left to right.

19. Chapter 4 – Slide 19 of 67 Names of Some Representative Elements Several groups of representative elements are known by common names. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

20. Chapter 4 – Slide 20 of 67 Alkali Metals Group 1A(1), the alkali metals, includes lithium, sodium, and potassium. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

21. Chapter 4 – Slide 21 of 67 Halogens Group 7A(17) the halogens, includes chlorine, bromine, and iodine. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

22. Chapter 4 – Slide 22 of 67 Identify the element described by the following: 1. Group 7A (17), Period 4 A) B) C) 2. Group 2A(2), Period 3 A) B) C) 3. Group 5A(15), Period 2 A) B) C) Learning Check

23. Chapter 4 – Slide 23 of 67 Carbon is a very special element. 1.Specialized industrial uses. elemental forms organic molecules such as solvents, fuels, pharmaceuticals, etc. 2.Central element in biomolecules found in living systems. Special Element: C

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27. Chapter 4 – Slide 27 of 67 Match the elements to the description: 1. Metals in Group 4A(14) A) B) C) 2. Nonmetals in Group 5A(15) A) B) C) 3. Metalloids in Group 4A(14) A) B) C) Learning Check

28. Chapter 4 – Slide 28 of 67 A closer look still

29. Chapter 4 – Slide 29 of 67 The Conjecture of Atoms As early as 500 B.C., Greek Philosophers proposed that all matter is made up of atoms –Atom: The smallest individual particle of an element that maintains the properties of that element Atomos - indivisible http://www.aperfectworld.org/clipart/science_technology/atom.gifhttp://members.aol.com/dcaronejr/ezmed/atom.jpg

30. Chapter 4 – Slide 30 of 67 Dalton’s Law of Atomic Theory 1.All matter is composed of extremely small particles called atoms. 2.Atoms of a given element are identical in their physical and chemical properties, while atoms of different elements differ in their physical and chemical properties. http://www.kjemi.uio.no/software/dalton/graphics/john_dalton.gif

31. Chapter 4 – Slide 31 of 67 Dalton’s Law of Atomic Theory 3. Atoms of different elements combine in simple, whole- number ratios to form compounds. 4. In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed. http://www.kjemi.uio.no/software/dalton/graphics/john_dalton.gif

32. Chapter 4 – Slide 32 of 67 Subatomic Particles Today, we know that atoms are made up of smaller, more fundamental particles called subatomic particles. Protons, Electrons & Neutrons

33. Chapter 4 – Slide 33 of 67 Subatomic Particles Atoms contains subatomic particles Protons have a positive (+) charge. Electrons have a negative (-) charge. Like charges repel and unlike charges attract. Neutrons are neutral. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

34. Chapter 4 – Slide 34 of 67 Rutherford’s Gold-Foil Experiment In Rutherford’s gold-foil experiment Positively charged particles were aimed at atoms of gold. Most went straight through the atoms. Only a few were deflected. Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close.

35. Chapter 4 – Slide 35 of 67 Rutherford’s Gold-Foil Experiment Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

36. Chapter 4 – Slide 36 of 67 Structure of the Atom An atom consists Of a nucleus that contains protons and neutrons. Of electrons in the large empty space around the nucleus. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

37. Chapter 4 – Slide 37 of 67 Atomic Mass Scale On the atomic mass scale for subatomic particles 1 atomic mass unit (amu) is equal to 1/12 of the mass of the carbon-12 atom. A proton has a mass of about 1 (1.007) amu. A neutron has a mass of about 1 (1.008) amu. An electron has a very small mass (0.00055 amu).

38. Chapter 4 – Slide 38 of 67 Particles in the Atom Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

39. Chapter 4 – Slide 39 of 67 The atomic number Is specific for each element. Is the same for all atoms of an element. Is equal to the number of protons in an atom. Appears above the symbol of an element in most periodic tables. Atomic Number 11 Na Atomic Number Symbol

40. Chapter 4 – Slide 40 of 67 Examples: Hydrogen has atomic number 1, every H atom has one proton. Carbon has atomic number 6, every C atom has six protons. Copper has atomic number 29, every Cu atom has 29 protons. Gold has atomic number 79, every Au atom has 79 protons. Atomic Numbers and Protons

41. Chapter 4 – Slide 41 of 67 Atomic Models Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

42. Chapter 4 – Slide 42 of 67 State the number of protons in each. 1. A nitrogen atom A) protons B) protons C) protons 2. A sulfur atom A) protons B) protons C) protons 3. A barium atom A) protons B) protons C) protons 4. A mercury atom A) protons B) protons C) protons Learning Check

43. Chapter 4 – Slide 43 of 67 An atom of any element is electrically neutral; the net charge of an atom is zero. In an atom, the number of protons is equal to the number of electrons. number of protons = number of electrons For example, an atom of aluminum has 13 protons and 13 electrons. The net charge is zero. 13 protons (13 +) + 13 electrons (13 -) = 0 What if there are more electrons than protons? or more protons than electrons? Electrons in An Atom

44. Chapter 4 – Slide 44 of 67 Mass Number The mass number Represents the number of particles in the nucleus. Is equal to the Number of protons + Number of neutrons

45. Chapter 4 – Slide 45 of 67 An atom has 14 protons and 20 neutrons. 1. Its atomic number is A) B) C) 2. Its mass number is A) B) C 3. The element is A) B) C) Learning Check

46. Chapter 4 – Slide 46 of 67 An atom of zinc has an atomic number of 30, and mass number of 65. 1. How many protons are in this zinc atom? A) B) C) 2. How many neutrons are in the zinc atom? A) B) C) 3. What is the mass number of a zinc atom that has 37 neutrons? A) B) C) Learning Check

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48. Chapter 4 – Slide 48 of 67 Isotopes Are atoms of the same element that have different mass numbers. Have the same number of protons, but different numbers of neutrons. Isotopes and Atomic Mass

49. Chapter 4 – Slide 49 of 67 A nuclear symbol (aka atomic symbol) Represents a particular atom of an element. Gives the mass number in the upper left corner and the atomic number in the lower left corner. Example: An atom of sodium with atomic number 11 and a mass number 23 has the following atomic symbol: mass number 23 Na atomic number 11 Nuclear Symbol

50. Chapter 4 – Slide 50 of 67 The nuclear symbol indicates the number of protons (p + ), neutrons, (n), and electrons (e - ) in a particular atom. 163165 O P Zn 81530 8 p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e - Information from Nuclear Symbols

51. Chapter 4 – Slide 51 of 67 Nuclear / Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Defines the element Charge = Number of protons - number of electrons

52. Chapter 4 – Slide 52 of 67 Nuclear / Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Charge = number of protons – number of electrons

53. Chapter 4 – Slide 53 of 67 Nuclear / Atomic Symbols X QA Z Mass number = number of protons + number of neutrons Atomic number = number of protons Charge = number of protons – number of electrons

54. Chapter 4 – Slide 54 of 67 Nuclear / Atomic Symbol Notation vs. The Periodic Table Notation Ca 2+ 40 20 Ca 40.078

55. Chapter 4 – Slide 55 of 67 Learning Check 1. Which of the following pairs are isotopes of the _________________? 2. In which of the following pairs do both atoms have _________________? A. 15 X 15 X 8 7 B. 12 X 14 X 6 6 C. 15 X 16 X 7 8

56. Chapter 4 – Slide 56 of 67 Atomic Mass The atomic mass of an element Is usually listed below the symbol of each element on the periodic table. Gives the mass of an “average” atom of each element compared to 12 C. Is not the same as the mass number. Na 22.99

57. Chapter 4 – Slide 57 of 67 Calculating Average Atomic Mass The calculation for the average atomic mass requires the Percent (%) abundance of each isotope. Atomic mass in amu of each isotope of that element. Sum of the weighted averages. mass isotope(1) x (%) + mass isotope(2) x (%) + … 100 100

58. Chapter 4 – Slide 58 of 67 Consider the element Magnesium

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61. Chapter 4 – Slide 61 of 67 Atomic Mass of Magnesium The atomic mass of Mg Is due to all the Mg isotopes. Is a weighted average. Is not a whole number. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

62. Chapter 4 – Slide 62 of 67 Calculating Atomic Mass Isotope Mass Abundance 24 Mg = 23.985 amu x 78.70/100 = 18.88 amu 25 Mg = 24.986 amu x 10.13/100 = 2.531 amu 26 Mg = 25.983 amu x 11.17/100 = 2.902 amu Atomic mass (average mass) Mg = 24.31 amu Mg 24.31

63. Chapter 4 – Slide 63 of 67 Atomic Mass for Cl The atomic mass of chlorine is the weighted average of two isotopes 35 Cl and 37 Cl. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

64. Chapter 4 – Slide 64 of 67 35 Cl has atomic mass 34.97 (75.76%) and 37 Cl has atomic mass 36.97 (24.24%). The atomic mass and percent of each isotope are used to calculate the contribution of each isotope to the weighted average. 34.97 x 75.76 = 26.49 amu 100 36.97 x 24.24 = + 8.962 amu 100 35.45 amu The sum is the weighted average or atomic mass of Cl. 35.45 amu Calculating Atomic Mass for Cl

65. Chapter 4 – Slide 65 of 67 Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.11% of 69 Ga (atomic mass 68.93) atoms and 39.89% of 71 Ga (atomic mass 70.93) atoms. What is the atomic mass of gallium? Learning Check →

66. Chapter 4 – Slide 66 of 67 69 Ga 68.93 amu x 60.11 = 41.43 amu (from 69 Ga) 100 71 Ga 70.93 amu x 39.89 = 28.29 amu (from 71 Ga) 100 Atomic mass Ga = 69.72 amu Solution 31 Ga 69.72

67. Chapter 4 – Slide 67 of 67 Examples of Isotopes and Their Atomic Masses Most elements have two or more isotopes that contribute to the atomic mass of that element. Table 4.8 Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings