2. The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: Dalton

3. Elements are substances that consist of just one type of atom- they cannot be broken down to other substances The basic unit of all matter is the atom, the smallest unit of matter that retains the properties of an element A Molecule is a substance containing 2 or more atoms A Compound is a substance containing 2 or more elements

4. Is brass an element? What about: Oxygen O 2 Water H 2 0 Helium He Is brass a molecule? Is brass a compound?

5. The structure of the atom ELECTRON – negative, orbits outside the nucleus PROTON – positive, also in nucleus NEUTRON – neutral, located in the NUCLEUS (center of atom)

6. The Atom Hydrogen Proton Electron Hydrogen has one proton, one electron and NO neutrons

7. The Atom Helium Electron Proton Neutron Helium has two electrons, two protons and two neutrons

8. The Atom Carbon Protons Neutrons Electrons Carbon has six electrons, six protons and six neutrons.

9. The Atom Nitrogen Protons Neutrons Electrons Nitrogen has seven electrons, seven protons and seven neutrons.

10. The Atom Oxygen Protons Neutrons Electrons Oxygen has eight electrons, eight protons and eight neutrons.

11. red and green are opposites

12. assume red and green cancel each other net color = neutral

13. take away one red

14. net color = 1 green

15. take away two red

16. net color = 2 green

17. net color = neutral

18. net color = 2 red

19. in this arrangement …

20. green is trapped inside. Only red balls can be added or taken away…

21. color = 2 green

22. color = 1 red

23. color = ?

24. 3 red

25. color = ?

26. 3 green

28. + the positive (+) particle is called a proton

29. the negative (-) particle is called an electron

30. +++++ positive and negative are opposites they cancel each other out

31. +++++ net charge = zero

32. +++++ in an atom, protons ( ) are in the center and electrons ( ) are on the outside +

33. +++++ only electrons ( ) can be added or taken away

34. +++++ this is an atom with 5 electrons and 5 protons

35. +++++ the atom is neutral net charge = zero

36. +++++ 5 (-) and 5 (+) = zero charge (neutral)

37. +++++ charge = ?

38. +++++ charge = 1- (one minus)

39. ++++ charge = ?

40. +++++ 2+ ( two plus )

41. WHEN REMOVING ELECTRONS

42. THE RESULTING CHARGE IS POSITIVE

43. WHEN REMOVING ELECTRONS THE RESULTING CHARGE IS POSITIVE neutral 1+

44. WHEN ADDING ELECTRONS

45. THE RESULTING CHARGE IS NEGATIVE WHEN ADDING ELECTRONS

46. THE RESULTING CHARGE IS NEGATIVE neutral 2 WHEN ADDING ELECTRONS

47. An atom with positive or negative charge is called an drum roll ION

49. Hydrogen atoms are very reactive…. Helium is not. Which do you think the Hindenburg was filled with? Atoms want 8 electrons in the outermost shell. If atoms have less than 8 then they react with other atoms to gain or lose electrons.

50. Ionic Bonds

51. Reacting with other atom can cause atoms to bond with each other. In an IONIC bond, electrons are lost or gained, resulting in the formation of IONS in ionic compounds. FK

52. FK + _ The compound potassium fluoride consists of potassium (K + ) ions and fluoride (F - ) ions

53. FK + _ The ionic bond is the attraction between the positive K + ion and the negative F - ion

55. Covalent Bonds

56. But rather than losing or gaining electrons, atoms now share an electron pair. In covalent bonding, atoms still want 8 electron in the outer shell

57. Cl 2 Chlorine forms a covalent bond with itself

58. Cl How will two chlorine atoms react?

59. Cl Each chlorine atom wants to gain one electron to achieve get 8

60. Cl 8

61. circle the electrons for each atom that completes their octets 8

62. Cl circle the electrons for each atom that completes their octets Each atom has 8 electrons by each atom sharing the electron pair in the middle

63. Cl circle the electrons for each atom that completes their octets It is called a SINGLE BOND

64. Cl circle the electrons for each atom that completes their octets Single bonds are abbreviated with a dash

65. O2O2 Oxygen

66. How will two oxygen atoms bond? OO

67. OO Each atom has two unpaired electrons

68. Both oxygen atoms want to gain two electrons. OO

69. 8 O O

70. 8 O O

71. two set of shared electrons, O O making a double bond

72. O O = For convenience, the double bond can be shown as two dashes. O O

73. O O = This is the oxygen molecule, O 2 this is so cool! !

74. Covalent bonding allows for an amazingly large variety of compounds such as

75. small compounds like water and carbon dioxide,

76. and alcohol (ethanol),

77. to larger compounds such as aspirin, (21 atoms)

78. to all of the 40,000 different proteins you have in your body, including

79. insulin, with about 900 atoms,

80. and hemoglobin, with about 11,000 atoms!

81. There are an estimated 10 40 possible compounds containing up to 50 atoms The known chemical world, including natural and synthetic compounds, is far far far below 1% of that. N ATURE volume 442 p. 502 3 August 2006