1. Chapter 4 “Chemical Foundations”

2. Section 4.1 Objective: to learn about relative abundance of the elements and learn some names of elements

3. The Elements Element Name Relative Abundance Oxygen Silicon Aluminum Iron Calcium Sodium Potassium Magnesium hydrogen 49.2% 25.7% 7.5% 4.71% 3.39% 2.63% 2.4% 1.93% 0.87%

4. How the Term Element is Used Could mean a single atom of that element ▫(Ar or H). Could mean molecules of an element ▫ (H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 ), which are found in their natural states. Could mean atoms of elements are present in some form ▫(sodium found in the human body). Look at each particular case to determine its proper use. 4

5. Section 4.2 Objective: to learn the symbols for the elements

6. 115 known: 88 found in nature, others are man made. Just as you had to learn the 26 letters of the alphabet before you learned to read and write, you need to learn the names and symbols of the chemical elements before you can read and write chemistry. 6

7. Names & Symbols One or two letter ▫Fluorine F Neon Ne First letter is CAPATALIZED, the second is not ▫Silicon Si Argon Ar Not always first two letters of element ▫Zinc Zn Chlorine Cl Sometimes based on other languages ▫ gold (aurum) Au Iron (ferrum) Fe

9. Law of Constant Composition A given compound always has the same composition, regardless of where it comes from.  Water always contains 8 g of oxygen for every 1 g of hydrogen.  Carbon dioxide always contains 2.7 g of oxygen for every 1 g of carbon. 9

10. Section 4.4 objective: to learn how a formula describes a compound's composition

11. Chemical Formulas Describe Compounds Compound – distinct substance that is composed of the atoms of two or more elements and always contains exactly the same relative masses of those elements. Chemical Formulas – expresses the types of atoms and the number of each type in each unit (molecule) of a given compound. 11

12. Rules for Writing Formulas 1.Each atom present is represented by its element symbol. 2.The number of each type of atom is indicated by a subscript written to the right of the element symbol. 3.When only one atom of a given type is present, the subscript 1 is not written. 12

13. Exercise The pesticide known as DDT paralyzes insects by binding to their nerve cells, leading to uncontrolled firing of the nerves. Before most uses of DDT were banned in the U.S., many insects had developed a resistance to it. Write out the formula for DDT. It contains 14 carbon atoms, 9 hydrogen atoms, and 5 atoms of chlorine. 13

14. C 14 H 9 Cl 5

15. Section 4.9 Objective: to understand diatomic molecules

16. Diatomic Molecules Most elements quite reactive ▫so they form compounds to become more stable ▫When found alone in nature, (not combined with other elements in compounds), these elements exist only as two covalently bonded atoms Some we give a special name to: ▫Diatomic molecules  Molecules made up of two atoms

17. Diatomic Molecules Nitrogen gas contains N 2 molecules. Oxygen gas contains O 2 molecules. Copyright © Cengage Learning. All rights reserved 17

18. Section 4.8 Objective: learn various features of the periodic table

19. Mendeleev’s Table Mendeleev arranged the elements in order of increasing relative atomic mass (protons had not been discovered yet). The elements on the modern periodic table are arranged in order of increasing atomic number. He also grouped elements with similar properties into columns and rows so that the properties of the elements varied in a regular pattern (periodically). 19 2 - Russian chemist Dmitri Mendeleev developed and published the basic arrangement of the periodic table between 1869 and 1871.

20. The Periodic Table: A Preview  A “periodic table” is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties  The periodic table allows you to easily compare the properties of one element to another

21. The Periodic Table: Row vs Group Each horizontal row (there are 7 of them) is called a period Each vertical column is called a group, or family Elements in a group have similar chemical and physical properties Identified with a number and either an “A” or “B”

22. Families Rare Earth Metals are the collective group of lanthanide and actinide series

23. 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 23 Periodic Table Helium Neon Argon Krypton Xenon

24. Metal vs Nonmetal vs Metalloid

25. Properties of Metals Efficient conductors of heat and electricity Malleable (hammered into thin sheets) Ductility (pulled into thin wires) Lustrous (shiny) appearance

26. Atoms

27. Sizing up the Atom  Elements are able to be subdivided into smaller and smaller particles – these are the atoms, and they still have properties of that element  If you could line up 100,000,000 copper atoms in a single file, they would be approximately 1 cm long  Despite their small size, individual atoms are observable with instruments such as scanning tunneling (electron) microscopes

28. 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 ▫atomic number Neutrons – ▫found in the nucleus ▫ no charge ▫ virtually same mass as a proton  -atomic mass p+n 28

29. The nucleus is:  Small compared with the overall size of the atom.  Extremely dense; accounts for almost all of the atom’s mass. 29

30. Subatomic Particles ParticleCharge Mass (g) Location Electron (e - ) (e - ) 9.11 x 10 -28 9.11 x 10 -28 Electron cloud Proton (p + ) +1 1.67 x 10 -24 1.67 x 10 -24Nucleus Neutron (n o ) (n o )0 1.67 x 10 -24 1.67 x 10 -24Nucleus

31. We have had many models of the atom (we will discuss this more in detail in a later chapter), but for now we will look at the Bohr Model and Lewis Dot Structures

32. Neil Bohr’s Atomic Model electrons orbit nucleus like planets around sun Example 1 (3D model) “Jimmy Neutron” Example 2 (2D model)

33. Atomic Number Atoms are composed of identical protons, neutrons, and electrons ▫ How then are atoms of one element different from another element? Elements are different because they contain different numbers of PROTONS The “atomic number” of an element is the number of protons in the nucleus

34. Atomic Number Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. Element # of protons Atomic # (Z) Carbon66 Phosphorus1515 Gold7979

35. Question: How do I know how many electrons each element has? 4 Be Beryllium 9.012 On the periodic table the ATOMIC NUMBER also tells you how many electrons there are Because: ▫ #of protons = # of electrons

36. Atoms have an overall neutral charge # of p+ = # of e- ▫number of protons equals the number of electrons example….helium has atomic number of 2 ▫Protons = +2 ▫Neutrons = 0 ▫Electrons= -2 --------------------- Total charge 0  Remember this is ONLY true on the periodic table.  It is not true in “real life”

37. Why do different atoms have different chemical properties? The chemistry of an atom arises from its electrons. Electrons are the parts of atoms that “intermingle” when atoms combine to form molecules. It is the number of electrons that really determines chemical behavior. Specifically VALENCE ELECTRONS 37

38. Valence Electrons Electrons found in the outermost energy level of an atom. ▫Determine:  1. Chemical properties  2. Atoms ability to form bonds Every atom has between 1 and 8 valence electrons Group number helps to determine valence electrons Stop Bohr model

39. Lewis Dot Structures What are the valence electrons? ▫They determine a elements unique properties ▫They are also the electrons that are used in bonding Only these outer electrons want to bond? Why? ▫all other electrons (in their energy levels) are happy ▫therefore scientists want to focus their attention on these specific electrons Lewis dot structures ▫ Show only the valence electrons How do we figure out the number of valence electrons? ▫ GROUP NUMBER

40. So where are the electrons? If Bohr model isn’t accurate and Lewis’s just shows us valence electrons where are the electrons exactly? MODERN ATMOIC THEORY ▫Electrons are found in orbitals/clouds (regions around the nucleus where the electrons are likely to be found) ▫best scientists can do is calculate chance of finding electron in certain place within an atom ▫Electron move very fast.

41. Modern Atomic Theory

42. Figuring out the number of protons, electrons, neutrons Determining subatomic particles in elements (GENERIC) Element symbol (X)  one/two/three letter symbol for element Atomic number (Z)  number of protons found in the element Mass number (A)  number of protons + the number of neutrons The periodic table will give you all the information you need in order to calculate protons, neutrons and electrons X Mass number Atomic number Subscript → Superscript →

43. 4 Be Beryllium 9.012 Atomic Number = Number of protons and number of electrons. On the periodic table all elements are neutral. Therefore p = e Average Atomic Mass Number = Number of protons and number of neutrons. Sometimes p = n Sometimes p = n Element Symbol = symbol for element: usually first letter or two letters of its name. However, not in all cases. WHY? Element Name = Full name of the element

44. Mass Number Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p + + n 0 Nuclide p+p+p+p+ n0n0n0n0 e-e-e-e- Mass # - Oxygen - 10 - 3342 - - 31 15 8 8 18 Arsenic 7533 75 Phosphorus 15 31 16

45. Symbols n Find each of these: a) number of protons b) number of neutrons c) number of electrons d) Atomic number e) Mass Number Br 80 35

46. Symbols n If an element has an atomic number of 34 and a mass number of 78, what is the: a) number of protons b) number of neutrons c) number of electrons d) complete symbol

47. Symbols n If an element has 91 protons and 140 neutrons what is the a) Atomic number b) Mass number c) number of electrons d) complete symbol

48. Symbols n If an element has 78 electrons and 117 neutrons what is the a) Atomic number b) Mass number c) number of protons d) complete symbol

49. Isotopes

50. Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers. These are called isotopes.

51. Isotopes Frederick Soddy (1877-1956) proposed the idea of isotopes in 1912 Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. (same P, different N) Soddy won the Nobel Prize in Chemistry in 1921 for his work with isotopes and radioactive materials.

52. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. IsotopeProtonsElectronsNeutronsNucleus Hydrogen–1 (protium) (protium)110 Hydrogen-2(deuterium)111 Hydrogen-3(tritium)112

53. Naming Isotopes We put the mass number after the name of the element: ▫ carbon-12 ▫ carbon-14 ▫ uranium-235

54. Isotopes Isotopes- an element with the different numbers of neutrons ▫Most element have a number of different isotopes  For example C-12, C-13, and C-14. We use C-14 to carbon date fossils ▫Scientists take an average of these atomic masses ▫ In this calculation the abundance of the isotope is also calculated  For example the atomic mass of C is 12.01 Can you hypothesize which C isotope is most abundant ▫ ***therefore rare isotopes have little effect on the atomic mass

55. Atomic MassesIsotopeSymbol Composition of the nucleus % in nature Carbon-12 12 C 6 protons 6 neutrons 98.89% Carbon-13 13 C 6 protons 7 neutrons 1.11% Carbon-14 14 C 6 protons 8 neutrons <0.01% Atomic mass is the average of all the naturally occurring isotopes of that element. Carbon = 12.011

56. Isotopes Elements occur in nature as mixtures of isotopes. Remember: Isotopes are atoms of the same element that differ in the number of neutrons.

57. 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 57

58. Remember an element is determined by the number of protons it has* What happens if you change the number of protons of an element? ▫ You have a completely different element What happens if you change the number of neutrons? ▫you still have same element but this element has a different number of neutrons then the original element…….  This is an isotope What happens if you change the number of electrons? ▫ You have the same element….but the element has a charge (either positive or negative)  This is called an ION

59. Ions

60. Are atoms of an element with an unequal number of protons and electrons Everything is based off the electron ion charge also called Oxidation Number Represented as Mg +2 or OH -1 ▫Cation = + ion (loses an electron, therefore has more protons (+) then electrons) ▫Anion = - ion (gains an electron, there has more electrons (-) then protons)

61. 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. 61 Ions

62. 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. 62 Ions

63. Oxidation Number *remember atoms want to be stable *everyone wants to be like the last column (noble gases) and have ______ valence electrons. Exceptions? How do atoms do this? ▫Atoms want to get to that stable outer valence shell of 8 electrons. Oxygen has ______ valence electrons; therefore it needs _____ more to get to eight. IF AN ATOM NEEDS TO GAIN ELECTRONS THE OXIDATION NMUMBER IS NEGATIVE. THE ATOM IS IN NEED. LIKE A DEBT……THE ATOM NEEDS MORE MONEY (electrons) If an atom needs 2 more electrons; its oxidation number is -2 (negative 2)If an atom needs 2 more electrons; its oxidation number is -2 (negative 2)

64. Fluorine has _________ valence electrons; therefore it needs ________ more to get to eight.

65. If an atom needs 1 more electron; its oxidation number is -1 (negative 1) Nitrogen has ________ valence electrons: therefore it needs _____ more to get to eight

66. If an atom needs 3 more electrons; its oxidation number is -3 (negative 3) NEXT Lithium has _____ valence electrons: how does it get to be stable?

67. What is easier to gain 7 electrons or get rid of one? IF AN ATOM HAS EXTRA ELECTRONS THE OXIDATION NUMBER IS POSITIVE. THE ATOM HAS MORE THEN IT NEEDS. LIKE A CREDIT……YOU HAVE EXTRA MONEY (ELECTRONS)TO LOAN Lithium has ________ valence electrons: therefore it can loan ______ more to become stable

68. What is easier to gain 7 electrons or get rid of one? IF AN ATOM HAS EXTRA ELECTRONS THE OXIDATION NUMBER IS POSITIVE. THE ATOM HAS MORE THEN IT NEEDS. LIKE A CREDIT……YOU HAVE EXTRA MONEY (ELECTRONS)TO LOAN Lithium has ________ valence electrons: therefore it can loan ______ more to become stable If an atom can loan 1 electrons; its oxidation number is +1 (positive 1)

69. There is a trend in the oxidation number on the periodic chart. Can you find it? Beryllium has ___________ valence electrons; therefore it can loan ________more to become stable. I f an atom can loan 2 electrons; its oxidation number is +2 (positive 2) Carbon has __________ valence electrons; it is right in the middle; therefore it can gain or loan 4 electrons 1... if an atom can gain OR loan 4 electrons; its oxidation number is +/- 4 (positive or negative 4)

70. Oxidation trend in the periodic table

71. Section 4.11 Objective: learn how ions combine to form neutral compounds

72. Ions combine to form ionic compounds. Properties of ionic compounds  High melting points  Conduct electricity  If melted  If dissolved in water Ionic compounds are electrically neutral. The charges on the anions and cations in the compound must sum to zero. 72 Compounds that Contain Ions

73. Formulas for Ionic Compounds Write the cation element symbol followed by the anion element symbol. The number of cations and anions must be correct for their charges to sum to zero. 73

74. This chapter will be referred to on a daily basis from here on out. If you do not know and understand this chapter YOU WILL BE LOST!