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Physical Science Unit 2 Review Lesson 1 Atoms Science Journals • Get out your science Journals • If you don’t have one use some blank paper and add it your journal later The Development of Atomic Theory What is an Atom? • An atom is the smallest particle that an element can be divided and still be that element. • For example the smallest particle of carbon is a single atom of carbon. If you divide it is no longer carbon anymore. PIECES OF CARBON CARBON ATOM What 3 new ideas did John Dalton propose about the atom? • All substances are made up of atoms which are small particles that cannot be created, divided, or destroyed. • Atoms of the same element are exactly alike and atoms of different elements are different. • Atoms join with other atoms to form different substances J.J. Thomson 1856-1940 • What particle did Thomson discover? J.J. Thomson discovered that atoms are made of smaller negativelycharged particles called electrons. • Thomson’s discovery was the result of doing experiments with “cathode ray tubes” Ernest Rutherford (1871 - 1937) • Awarded the Nobel Prize in Chemistry for his discovery of alpha particles, positively charged particles emitted from radioactive elements • Was a student of J.J. Thomson but disagreed with the “Plum Pudding Model” • Devised an experiment to investigate the structure of positive and negative charges in the atom. Rutherford’s Revised Atomic Theory (1911) Result: Most of the positively charged particles went straight through the gold foil. Atomic Theory: Most of the matter of the atom is found in a very small part of the atom. This is called the nucleus of the atom. It is very tiny and extremely dense. Result: Some of the positively charged particles were deflected or even bounced back. Atomic Theory: Like charges repel so the nucleus must have a positive charge. If electrons have a negative charge they could not be in a positively charged nucleus. Electrons must surround the nucleus at a distance. Result: The diameter of the nucleus is 100,000 times smaller than the diameter of the entire gold atom. Atomic Theory: Atoms are mostly empty space with a tiny, massive nucleus at the center . The Bohr Model of the Atom What did Bohr learn about electron movement? • Bohr proposed that electrons move in paths at certain distances around the nucleus. • Electrons can jump from a path on one level to a path on another level. • Click here http://www.colorado.edu/p hysics/2000/quantumzone/ bohr.html The Modern Theory of the Atom • Electrons travel in regions called “electron clouds” • You cannot predict exactly where an electron will be found http://www.fearofphysics.com/Atom/atom3.html Energy Levels The energy that an electron has is based on its location around the nucleus. (Electrons that are closer to the nucleus have less energy than those that are farther away from the nucleus) Lesson 2 • Atoms Number • Atomic Mass • Parts of a atom Subatomic Particles Particle Symbol Charge Relative Mass 0 Electron e- 1- Proton p+ + 1 Neutron n 0 1 Location of Subatomic Particles 10-13 cm electrons nucleus protons neutrons 10-8 cm 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) 6 6 Phosphorus 15 15 Gold 79 79 Carbon Atomic Number on the Periodic Table Atomic Number Symbol 11 Na 16 Learning Check State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons 17 Solution State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons 19 Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons 20 Mass Number Mass number is the number of protons and neutrons in the nucleus of an isotope. Mass number is determined by rounding the atomic mass to the nearest whole # 16 Arsenic 8 75 Phosphorus 16 8 16 33 75 15 31 Mass # = p+ + no Lesson 4 Periodic Table • Since Lesson 3 was a open lesson Dmitri Mendeleev In 1869 he published a table of the elements organized by increasing atomic mass. • http://science.howstuf fworks.com/periodictable-videosplaylist.htm 1834 1907 How do you read the PERIODIC TABLE? How do I find the number of protons, electrons, and neutrons in an element using the periodic table? o # of PROTONS = ATOMIC NUMBER o # of ELECTRONS = ATOMIC NUMBER o # of NEUTRONS = ATOMIC _ ATOMIC WEIGHT NUMBER Lesson 5 • Design of Periodic Table The horizontal rows of the periodic table are called PERIODS. The elements in any group of the periodic table have similar physical and chemical properties! The vertical columns of the periodic table are called GROUPS, or FAMILIES. Lesson 6 Molecules • Linking atoms together Atom – the smallest unit of matter “indivisible” Helium atom electron shells a) Atomic number = number of Electrons b) Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. c) Electron shells determine how an atom behaves when it encounters other atoms Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to Gain 4 electrons N would like to Gain 3 electrons O would like to Gain 2 electrons Why are electrons important? 1) Elements have different electron configurations different electron configurations mean different levels of bonding Electrons are placed in shells according to rules: 1) The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons. Lesson 7 • • • • • State of Matter Solid Liquid Gas Any element can be in a different state of matter depending on the amount of energy. Lesson 8 • Physical and Chemical Changes • Physical change is a change in the state of Matter • Chemical change is a change in the molecules to make different molecules. Examples of Physical Change • Ice melting • Kool Aid mixing into water • Chat some other examples Chemical changes • • • • Food cooking Chemicals the make electricity ie batteries Metal rusting Vinegar and baking soda • Chat me some more examples Be sure to review notes • Read over your science journal • Then complete the review and move on the Unit Assessment • We start Unit 3 next week.