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Subatomic particles Electron Proto n Neutro n Nam e SymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n0 +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10.

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Presentation on theme: "Subatomic particles Electron Proto n Neutro n Nam e SymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n0 +1 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10."— Presentation transcript:

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3 Subatomic particles Electron Proto n Neutro n Nam e SymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n / x x

4 Counting the Pieces Atomic Number = number of protons in the nucleus # of protons determines kind of atom (since all protons are alike!) the same as the number of electrons in the neutral atom. Mass Number = the number of protons + neutrons. These account for most of mass

5 Counting the Pieces Protons: equal to atomic number Neutrons: Mass Number – Atomic Number Electrons: In a neutral atom equal to atomic number

6 Symbols Contain the symbol of the element, the mass number and the atomic number.

7 Symbols Contain the symbol of the element, the mass number and the atomic number. X Mass number Atomic number

8 Symbols Find the number of protons number of neutrons number of electrons Atomic number Mass Number F 19 9

9 Symbols n Find the –number of protons –number of neutrons –number of electrons –Atomic number –Mass Number Br 80 35

10 Symbols n if an element has an atomic number of 34 and a mass number of 78 what is the –number of protons –number of neutrons –number of electrons –Complete symbol

11 Symbols n if an element has 91 protons and 140 neutrons what is the –Atomic number –Mass number –number of electrons –Complete symbol

12 Symbols n if an element has 78 electrons and 117 neutrons what is the –Atomic number –Mass number –Number of protons –Complete symbol

13 What if Atoms Arent Neutral Ions: charged atoms resulting from the loss or gain of electrons

14 What if Atoms Arent Neutral Anion: negatively charged ion; result from gaining electrons Take the number of electrons in a neutral atom and add the absolute value of the charge Br 1- Identify: Number of Protons Number of Neutrons Number of Electrons

15 What if Atoms Arent Neutral Cation: positively charged ion; result from the loss of electrons Take the number of electrons in a neutral atom and subtract the value of the charge Al 3+ Identify: Number of Protons Number of Neutrons Number of Electrons

16 Isotopes Atoms of the same element can have different numbers of neutrons Different mass numbers Called isotopes

17 Naming Isotopes We can also put the mass number after the name of the element. carbon- 12 carbon -14 uranium-235

18 Atomic Mass How heavy is an atom of oxygen? There are different kinds of oxygen atoms We are more concerned with average atomic mass Average atomic mass is based on abundance of each element in nature. We dont use grams because the numbers would be too small

19 Measuring Atomic Mass Unit is the Atomic Mass Unit (amu) It is one twelfth the mass of a carbon- 12 atom Each isotope has its own atomic mass, thus we determine the average from percent abundance

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21 Pure Substances Cannot be physically separated Every sample has the same characteristics and they can be used to identify a substance

22 Elements Are made up of ONE type of atom Atoms are the smallest unit of an element that maintains the chemical identity of that element They can be found on the Periodic Table Examples: Carbon, Nitrogen, Calcium

23 Compounds Can be broken down into simple stable substances Are made up of two or more types of atoms that are chemically bonded Examples: Water (H 2 O), sugar (C 12 H 22 O 11 )

24 Mixtures A blend of two or more kinds of matter, each which retains its own identity and properties

25 Homogeneous Mixtures Have uniform composition Also known as SOLUTIONS Examples: salt water, tea

26 Solutions ALLOYS are solid solutions that contain at least 1 metal They are blended together so that they have more desirable properties Some alloys you may know are: Stainless Steel: iron, chromium, and zinc Brass: zinc and copper Bronze: tin and copper Sterling Silver: copper and silver

27 Heterogeneous Mixtures Do not have uniform composition You can see the particles in them Examples: Sand on the beach (contains sand, shells, rocks, bugs, etc) Soil (contains dirt, rocks, worms, etc) Chicken Soup (contains water, chicken, veggies etc)

28 Suspensions A heterogeneous mixture where the solid particles eventually settle out of solution Examples: Muddy water Mixtures of two solids Paint

29 Properties of Matter All pure substances have characteristic properties Properties are used to distinguish between substances Properties are also used to separate substances

30 Physical Properties A Physical Property is a characteristic that can be observed or measured without changing the composition of the substance Physical properties describe the substance itself Examples Physical State Color Mass, shape, length Magnetic properties

31 Chemical Properties A Chemical Property indicates how a substance will react with another Chemical properties cannot be determined without changing the identity of the substance Examples: Iron Rusting Silver Tarnishing

32 Physical Changes A Physical Change is a change in a substance that does not alter the substances identity Examples: Grinding Cutting Melting Boiling

33 Chemical Changes A change in which one or more substances are converted into different substances is called a Chemical Change Signs of a Chemical Change: Color Change Gas is Released Temperature Change Precipitate – Solid falls out of solution Substance Disappears

34 How Atoms Combine Two or more atoms that are chemically combined make up a compound The combination results in a chemical bond, a force which holds elements together in a compound

35 Covalent Bonds Covalent Bonds are formed when atoms in a compound share electrons Molecule – two or more atoms held together by a covalent bond Usually occurs between nonmetals

36 Covalent Bonding in Water

37 Ions An atom that has gained or lost an electron is called an ion. Multiple atoms can combine to form an ion – called a Polyatomic Ion Silicate (SiO 4 4- ) and Carbonate (CO 3 2- ) are important in forming materials at Earths Surface

38 Ionic Bonding Positive and negative ions attract each other Ionic Bonds occur when oppositely charged ions form a compound Usually consist of 1 metal and 1 nonmetal Positive ion written first in chemical formula (NaCl) Ionic compounds have a neutral charge

39 Ionic Bonding in NaCl

40 Metallic Bonds Metals share valence electrons between all atoms Like a group of positive ions in a sea of electrons

41 Atomic Theory and Structure

42 Democritus Democritus added: Matter is composed of atoms which move through empty space Atoms are solid, homogeneous, indestructible, and indivisible Different atoms have different shapes and sizes The size, shape, and movement of atoms determine their properties

43 Leading to the modern theory Late 1700s - John Dalton- England. Teacher- summarized results of his experiments and those of others. Daltons Atomic Theory Combined ideas of elements with that of atoms. Saw atoms as small solid spheres. Billiard Ball Model.

44 Daltons Atomic Theory All matter is made of tiny indivisible particles called atoms. Atoms of the same element are identical, those of atoms of different elements are different. Atoms of different elements combine in whole number ratios to form compounds. Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

45 Law of Conservation of Mass The law of conservation of mass states that matter is neither created nor destroyed in chemical reactions

46 Discovery of the Electron J. J. Thomson - English physicist Made a piece of equipment called a cathode ray tube. It is a vacuum tube - all the air has been pumped out.

47 Thomsons Experiment Voltage source +- Vacuum tube Metal Disks

48 Thomsons Experiment Voltage source +-

49 Thomsons Experiment Voltage source +-

50 Thomsons Experiment Voltage source +-

51 n Passing an electric current makes a beam appear to move from the negative to the positive end Thomsons Experiment Voltage source +-

52 n Passing an electric current makes a beam appear to move from the negative to the positive end Thomsons Experiment Voltage source +-

53 n Passing an electric current makes a beam appear to move from the negative to the positive end Thomsons Experiment Voltage source +-

54 n Passing an electric current makes a beam appear to move from the negative to the positive end Thomsons Experiment Voltage source +-

55 Thomsons Experiment By adding an electric field

56 Voltage source Thomsons Experiment n By adding an electric field + -

57 Voltage source Thomsons Experiment n By adding an electric field + -

58 Voltage source Thomsons Experiment n By adding an electric field + -

59 Voltage source Thomsons Experiment n By adding an electric field + -

60 Voltage source Thomsons Experiment n By adding an electric field + -

61 Voltage source Thomsons Experiment n By adding an electric field he found that the moving pieces were negative + -

62 Plum Pudding Model Proposed by JJ Thomson Said the atom had a uniform positive charge in which the negatively charged electrons resided

63 Lead block Uranium Gold Foil Fluorescent Screen

64 He Expected The alpha particles to pass through without changing direction very much. Because…? …the positive charges were thought to be spread out evenly. Alone they were not enough to stop the alpha particles.

65 What he expected

66 Because

67 He thought the mass was evenly distributed in the atom

68 Since he thought the mass was evenly distributed in the atom

69 What he got

70 How he explained it + Atom is mostly empty. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough.

71 +

72 The Bohr Ring Atom n = 3 n = 4 n = 2 n = 1

73 Electron Cloud Theory

74 What are acids and bases? ACIDS BASES TASTESOURBITTER FEEL STINGSSLIPPERY REACTIONS YES / METAL NO / METALS CONDUCTS ELECTROLYTE ELECTROLYTE RELEASES H + OH -

75 HOW DO WE MEASURE ACIDS AND BASES? INDICATORS A SUBSTANCE THAT TURNS ONE COLOR IN AN ACIDIC SOLUTION AND ANOTHER COLOR IN A BASIC SOLUTION SOME INDICATORS ARE: LITMUS: DYE THAT COMES FROM A LICHEN PHENOLPHTHALEIN: INDICATES ONLY BASES UNIVERSAL INDICATOR: ACID, NEUTRALS, BASES CABBAGE JUICE: ACIDS, NEUTRAL, BASE


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