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PASS Content Standard 1.1 Matter is made up of minute particles called atoms, and atoms are composed of even smaller components (i.e. protons neutrons and electrons). QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Inertia - 7 min Matter is anything that has inertia. The resistance of an object to a change in motion. If an object is at rest, a force is needed to make it move. If an object is moving, a force is needed to slow it. Atoms are so small that, even today, direct visual inspection is all but impossible. Our model of the atom changes as our experimental ability improves. Greek philosopher around the year 400 BC. Proposed that matter could not be divided into smaller and smaller pieces forever. Used the word atomos to describe the smallest possible piece of matter. An English chemist who proposed the first atomic theory in 1803. 1. All elements are composed of indivisible particles. 2. Atoms of the same element are exactly alike. 3. Atoms of different elements are different. 4. Compounds are formed by joining two or more elements. Only one of his points was incorrect - which one? 1. All elements are composed of indivisible particles. 2. Atoms of the same element are exactly alike. 3. Atoms of different elements are different. 4. Compounds are formed by joining two or more elements. 1. All elements are composed of indivisible particles. 2. Atoms of the same element are exactly alike. 3. Atoms of different elements are different. 4. Compounds are formed by joining two or more elements. The English scientist who discovered electrons in 1897. Sometimes called the "plum pudding" model. Thomson thought of an atom as being composed of positively charged material with the negatively charged electrons scattered through it. The British physicist who discovered the nucleus in 1908. Rutherford proposed an atom that is mostly empty space. There is a small, positive nucleus with negative electrons scattered around the outside edge. The Danish scientist who proposed the Planetary Model in 1913. Electrons move in definite orbits around the nucleus, like planets moving around the Sun. QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Bohr Model - 5 min Can you identify the element represented here? Neon Since 1935, many physicists have contributed to the development of "Quantum Mechanics" QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. Quantum mechanics - 3 min Quarks were "invented" by Murray Gell-Mann and George Zweig at Caltech in 1964. The idea of quarks was not taken seriously at first. But experiments in the 1970s began to provide evidence supporting their existence. The quark model is the best theory we have today to describe the structure of atoms and molecules. Up Down Charm Strange Top Bottom 2 + /3 - 1/3 + 2/3 - 1/3 + 2/3 1 - /3 Quarks are so small that they could probably travel through a mile and a half of lead without hitting another particle. Quarks cannot exist by themselves. Quarks must be bound to other quarks by the exchange of gluons. "Lightweight" particles not composed of quarks. Electrons are leptons with a mass of -31 9.1 X 10 kilograms. "Heavy" particles composed of 3 quarks. Protons are baryons composed of 2 Up quarks and 1 Down quark. Protons have a mass of -27 1.67 X 10 kilograms. "Heavy" particles composed of 3 quarks. Neutrons are baryons composed of 2 Down quarks and 1 Up quark. Neutrons have a mass of -27 1.67 X 10 kilograms. Bosons are "force" carriers. It is the exchange of these particles between fundamental particles that allows the formation of more massive particles. Photon - electromagnetic force Gluon - strong nuclear force + o W , W , and Z - weak nuclear force Graviton - gravity The graviton is the only force-carrying particle that has not been observed, either directly or indirectly. Antiparticles have exactly the same mass but opposite charges. Leptons and quarks have anti-particles. Bosons do not have anti-particles. Today's atomic model explains the structure of atoms using: 6 types of quarks 6 types of leptons 4 types of force carriers Basic Subatomic Particles Electrons have a negative charge and are found in energy levels outside the nucleus. Protons have a positive charge and are found in the nucleus. Neutrons do not have a charge and are found in the nucleus. Basic Subatomic Particles The number of electrons and protons in a normal atom is equal, giving the atom an overall neutral charge. All the atoms of an element have the same number of protons, indicated by the atomic number on the periodic table. Most elements have "isotopes", atoms with different numbers of neutrons Basic Subatomic Particles An atom's valence electrons (outer energy level) are easily changed during chemical reactions. Atoms that have gained or lost valence electrons are called "ions". Protons and neutrons in the nucleus are never changed during chemical reactions. End Content Standard 1.1 Review Physical Science Content Standard 1.1 1. What is science? 2. What is truth? 3. What are the steps of the scientific method, beginning with the first step? 4. What is a hypothesis? 5. What is the purpose of an experiment? 6. What is chemistry? 7. What is physics? 8. What is matter? 9. What is inertia? 10. What is needed to make an object at rest begin to move? 11. What is Democritus known for? 12. Who proposed the first atomic theory? 13. How many points did Dalton's theory have? 14. What is J.J. Thomson known for? 15. Who discovered the nucleus of atoms? 16. What do we commonly call Bohr's model of an atom? 17. Who discovered the neutron? 18. What subatomic particles did Gell-Mann and Zweig "invent"? 19. What are the 6 flavors of quarks? 20. What is a lepton? 21. What is the mass of an electron? 22. What is a boson? 23. What is the mass of a proton? 24. What is a baryon? 25. What do we call an atom with a charge? 26. What are isotopes? 27. Where are valence electrons found? 28. An atom has 9 protons and an atomic mass of 19. How many neutrons does it have? 29. What are antiparticles? 30. Which type of boson has never been observed? Tomorrow's test will have 20 fill in the blank questions.