2. Unit 4 (Ch. 11 and 12):Atoms, Elements, and The Periodic Table Table of Contents Essential Question: How was our current model of the atom developed? *people involved *ideas they created

3. GPS Standards: Table of Contents S8P1 – The Nature of Matter 1a. – Atoms versus Molecules 1b. - Elements vs. Compounds vs. Mixtures 1f. - Periodic Table 1g. – Law of Conservation of Matter

4. Chapter 11 - Structure of Matter Lesson Objectives: 1.Define matter 2.Explain what the Law of Conservation of Matter means. 3.Describe the historical views of the atom and how its look changed over time. 4. Define the Atomic Theory of Matter.

5. Matter is anything that has mass and takes up space. Even though you can’t see it or hold it in your hand, air is matter (has mass and takes up space). What is matter? Structure of Matter 1 1 Light and heat do not take up space, and they have no mass. Therefore, they are not forms of matter.

6. What is matter? Structure of Matter 1 1

7. Democritus was a Greek philosopher who thought the universe was made of empty space and tiny bits of “stuff”. He believed that the bits of stuff were so small they could no longer be divided into smaller pieces. He called these tiny pieces “atomos” or atoms. What makes up matter?— An Early Idea Structure of Matter Today an atom is defined as a small particle that makes up all types of matter.

8. Democritus’s ideas about atoms were a first step toward understanding matter. It wasn’t until the early 1800s (nearly 2000 years later) that scientists built upon the concept of atoms to form the current atomic theory of matter. What makes up matter?— An Early Idea Structure of Matter However, most scientists did not believe in his ideas because atoms could not be seen.

9. People once thought matter could appear and disappear because of the changes they saw as matter burned or rusted. What makes up matter?— An Early Idea Structure of Matter

10. Law of Conservation of Matter Structure of Matter Lavoisier, a French chemist who lived about 2,000 years after Democritus, showed that wood and the oxygen it combines with during burning have the same mass as the ash, water, carbon dioxide, and other gases that are produced.

11. which states that matter is not created or destroyed—it only changes form. From Lavoisier’s work came the Law of Conservation of Matter, In a similar way, an iron bar, oxygen, and water have the same mass as the rust that forms when they interact. Law of Conservation of Matter Structure of Matter

12. Atoms are so small it would take about 1 million of them lined up in a row to equal the thickness of a human hair. No matter what kind of model you use to picture it, the result is the same — an atom is an extremely small particle of matter. Modeling An Atom Structure of Matter Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily.

13. Modern Model of An Atom Where did this model come from? All atom models are scientific theories.

14. Models of the Atoms Thompson Rutherford Bohr 1 Bohr 2

15. Dalton believed that matter was made of atoms that were too small to be seen by the human eye. John Dalton’s Atomic Model Structure of Matter 1766 - 1844 He also thought that each type of matter was made of only one kind of atom.

16. John Dalton’s Atomic Model Structure of Matter Because predictions using Dalton’s model were supported by data, the model became known as the Atomic Theory of Matter.

17. J.J. Thomson, an English scientist, conducted experi- ments using a cathode ray tube. J.J. Thompson’s Atomic Model – Discovering Electrons Structure of Matter 1856 - 1940

18. J.J. Thompson’s Atomic Model Structure of Matter When he saw that the rays traveled toward a positively charged plate, he concluded that the cathode rays were made up of negatively charged particles. During his experiments, Thomson observed rays that traveled from the cathode to the anode.

19. Thomson had shown through his experi- ment that atoms are not too tiny to divide after all. J.J. Thompson’s Atomic Model Structure of Matter They are made up of even smaller subatomic particles such as the negatively charged ones he called electrons.

20. J.J. Thompson’s Atomic Model Structure of Matter Thompson believed that the electrons were embedded in a ball of positive charge

21. Models of the Atoms Thompson Rutherford Bohr 1 Bohr 2

22. In about 1910, a team of scientists led by Ernest Rutherford bombarded an extremely thin piece of gold foil with alpha particles. Ernest Rutherford’s Atomic Model —Discovering The Nucleus Structure of Matter Alpha particles are tiny, high- energy, positively charged particles that he predicted would pass through the foil. 1871 - 1937

23. Most of the particles passed straight through the foil as if it were not there at all, however, other particles changed direction, and some even bounced back. Rutherford’s Atomic Model Structure of Matter Rutherford concluded that because so many of the alpha particles passed straight through the gold foil, the atoms must be made of mostly empty space.

24. Rutherford’s Atomic Model Structure of Matter However, because some of the positively charged alpha particles bounced off something, the foil atoms must contain some positively charged object concentrated in the midst of this empty space. Rutherford called the positively charged, central part of the atom the nucleus.

25. Rutherford’s Atomic Model Structure of Matter He named the positively charged particles in the nucleus protons. He also suggested that electrons were scattered in the mostly empty space around the nucleus.

26. Models of the Atoms Thompson’s Model Rutherford’s Model

27. After the collisions, the nuclei seemed to be heavier –Rutherford didn’t know why. Sir James Chadwick - Discovering Neutrons Structure of Matter Sir James Chadwick, a student of Rutherford’s, suggested that the alpha particles themselves were not heavier, but the atoms had given off new particles. 1891 - 1974 He said that these uncharged particles came from the nucleus and he called them neutrons.

28. Early in the twentieth century, a scientist named Niels Bohr found evidence that electrons in atoms are arranged according to energy levels. Niels Bohr’s Atomic Model Structure of Matter The lowest energy level is closest to the nucleus and can hold only two electrons. 1885 - 1962

29. Niels Bohr’s Atomic Model Structure of Matter Higher energy levels are farther from the nucleus and can hold more electrons.

30. Models of the Atoms

31. Improving the Atomic Model Structure of Matter Some scientists thought that the electrons might orbit an atom’s nucleus in paths that are specific distances from the nucleus, similar to how the planets orbit the Sun.

32. Scientists now realize that electrons move in what is called the atom’s electron cloud. The Modern Atomic Model Structure of Matter Click image to view movie.

33. The electron cloud is a spherical cloud of varying density surrounding the nucleus. The Modern Atomic Model Structure of Matter The varying density shows where an electron is more or less likely to be.

34. The Modern Atomic Model Structure of Matter Atoms with electrons in higher energy levels have electron clouds of different shapes. Generally, the electron cloud has a radius 10,000 times that of the nucleus.

35. By the 1930s, it was recognized that matter was made up of atoms, which were, in turn, made up of protons, neutrons, and electrons. The Modern Atomic Model Structure of Matter Today, physicists have succeeded in breaking down protons and neutrons into even smaller particles called quarks.

36. These particles can combine to make other kinds of tiny particles, too. The Modern Atomic Model Structure of Matter The six types of quarks are up, down, strange, charmed, top, and bottom.

37. Models of the Atoms Thompson Rutherford Bohr 1 Bohr 2

39. Chapter 12 - Elements (The Simplest Matter) Lesson Objectives: 1. Describe how to read the periodic table. 2. Describe metals, non-metals, and metalloids. 3. Practice finding atomic information using the mass and atomic number of an element. 4. Define the term isotope.

40. Elements — One Kind of Atom An element is matter made of only one kind of atom. At least 109 elements are known and about 90 of them occur naturally on Earth. The Simplest Matter Examples of naturally occurring elements include the oxygen and nitrogen in the air you breathe and the metals gold, silver, aluminum, and iron.

41. Elements — One Kind of Atom The other elements are known as synthetic elements. These elements have been made in nuclear reactions by scientists with machines called particle accelerators (atom smashers) The Simplest Matter Some synthetic elements have important uses in medical testing and are found in smoke detectors and heart pacemaker batteries.

42. The Simplest Matter http://www.bulloch.k12.ga.us/sbms/

43. The Simplest Matter

45. Elements versus Compounds Examples: H 2 N 2 O 3 C 4 Examples: H 2 O NO 2 CO 2 C 6 H 12 O 6

46. The Periodic Table of Elements The Simplest Matter Chemists use a chart called the Periodic Table of Elements to help them organize and display the elements based on their properties. Each element is represented by a chemical symbol that contains one to three letters. The symbols are a form of chemical shorthand.

48. Periodic Table of Elements

49. Dmitri Mendeleev (1834 – 1907) Russian scientist was the first person to organize elements in a table according to their properties

50. Mendeleev’s First Table

51. Mendeleev’s Table

53. The Periodic Table The Simplest Matter The elements are organized on the periodic table by their properties. There are rows and columns that represent relationships between the elements. The rows in the table are called periods. The elements in a row have the same number of energy levels.

54. The Simplest Matter The columns are called groups. The elements in each group have similar properties related to their structure. They also tend to form similar properties related to their structure. They also tend to form similar bonds. The Periodic Table

56. Identifying Characteristics The Simplest Matter Each element is different and has unique properties. These differences can be described in part by looking at the relationships between the atomic particles in each element.

57. Metals generally have a shiny or metallic luster and are good conductors of heat and electricity. Classification of Elements The Simplest Matter Elements fall into three general categories — metals, metalloids, and nonmetals. All metals, except mercury, are solids at room temperature.

58. Classification of Elements The Simplest Matter 2 2 Metals are malleable, which means they can be bent and pounded into various shapes. Metals are also ductile, which means they can be drawn into wires without breaking. Most of the elements are metals.

59. Classification of Elements The Simplest Matter Nonmetals are elements that are usually dull in appearance. Most are poor conductors of heat and electricity. Many are gases at room temperature, and bromine is a liquid.

60. Classification of Elements The Simplest Matter The solid nonmetals are generally brittle, meaning they cannot change shape easily without breaking. The nonmetals are essential to the chemicals of life. More than 97 percent of your body is made up of various nonmetals. Except for hydrogen, the nonmetals are found on the right side of the periodic table.

61. Classification of Elements The Simplest Matter Metalloids are elements that have characteristics of metals and nonmetals. All metalloids are solids at room temperature. Some metalloids are shiny and many are conductors, but they are not as good at conducting heat and electricity as metals are.

62. On the periodic table, the top number is the element’s atomic number. Atomic Information The Simplest Matter Cl is the symbol for chlorine. The atomic number tells you the number of protons and electrons in a neutral atom of that element.

63. The Simplest Matter Atomic Information *remember the APE* Atomic Number - # of Protons - # of Electrons Chlorine (element #17) has 17 protons and 17 electrons

64. The Simplest Matter Atomic Information *remember the APE* Atomic Number = # of Protons and # of Electrons 1. How many protons and electrons would be in an atom of lead (element #82)? 3. How many protons and electrons would be in an atom of hydrogen (element #1)? 2. How many protons and electrons would be in an atom of calcium (element #20)? 82 20 1

65. The Simplest Matter Atomic Information The bottom number shows an atom’s mass number and is the number of protons plus the number of neutrons in the atom’s nucleus. The mass number for chlorine is 35 (round to nearest whole number) unit = amu (atomic mass unit)

66. The Simplest Matter Atomic Information – Finding Neutrons *remember the APE* Atomic Number = # of Protons and # of Electrons Mass number = # of protons + # of neutrons Mass number – Atomic number = # of neutrons

67. The Simplest Matter Atomic Information – Finding Neutrons *remember the A = atomic # P = protons E = electrons M = mass # -A = atomic # N = neutrons

68. Atomic Information *remember the APE* Atomic Number = # of Protons and - # of Electrons Mass number = # of protons + # of neutrons Mass number – Atomic number = # of neutrons Sample Problem : Nitrogen (N)-refer to the periodic table Atomic # = Mass # = # of protons = # of electrons = # of neutrons = 14 7 7 7 7 APEMANAPEMAN

69. Atomic Information *remember the APE* Atomic Number = # of Protons and - # of Electrons Mass number = # of protons + # of neutrons Mass number – Atomic number = # of neutrons Sample Problems: Oxygen (O)-refer to the periodic table Atomic # = Mass # = # of protons = # of electrons = # of neutrons = 16 8 8 8 8 APEMANAPEMAN

70. Atomic Information *remember the APE* Atomic Number = # of Protons and - # of Electrons Mass number = # of protons + # of neutrons Mass number – Atomic number = # of neutrons Sample Problems: Gold (Au) - refer to the periodic table Atomic # = Mass # = # of protons = # of electrons = # of neutrons = 197 79 118 79 APEMANAPEMAN

71. Today’s Essential Questions: What are isotopes?

72. Isotopes The Simplest Matter Although the number of protons changes from element to element, every atom of the same element has the same number of protons. However, the number of neutrons can vary even for one element. These are called isotopes, which are atoms of the same element that have different numbers of neutrons.

73. Isotopes The Simplest Matter Carbon (12) 6P 6E 6N Carbon (13) 6P 6E 7N Carbon (14) 6P 6E 8N

74. Isotopes The Simplest Matter Hydrogen has three isotopes with mass numbers of 1, 2, and 3. Each hydrogen atom always has one proton, but in each isotope the number of neutrons is different.