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The Structure of Matter (Science 10 Review) The Atom Do Now Place your lab safety contract into the blue bin (by station 8). Pick-up both a work booklet and a periodic table (by station 5) Plan for the Week Science 10 Review What is an element? Atom? Neutron? Proton? Electron? Bohr and Lewis Dot Diagrams Look at why we often need to dissolve things in water to do chemical reactions Differences between electrolytes and non electrolytes The Plan Explain how science & technology have influenced, & been influenced by historical development & societal needs. 1. Science 10 chemistry review 2. Learn about atoms & how to diagram them Bohr diagram Lewis dot diagram 3. Practice drawing a diagram of an atom Lab Safety Rap Elements A pure substance cannot be broken down into simpler substances by chemical means. You find these on the periodic table. The smallest part of an element is an atom. Atom The basic unit of matter. It is made up of Protons – positively charged particles located in the nucleus of an atom (p+). Neutrons – a neutral particle located in the nucleus of an atom (no). Electrons – a negatively charged particle located in the region surrounding the nucleus of an atom (e-). Atoms Protons Neutrons Electrons Atoms Particle Location Charge Proton Nucleus 1+ Neutron Nucleus 0 Electron Surrounding Nucleus 1– Joke for the Day A neutron walks into a bar, sits down and asks for a drink. Finishing, the neutron asks "How much?" The bartender says, "For you, no charge." Atoms Atomic Number – this is the number of protons within the atoms. Hydrogen has an atomic number of 1 which means that it has 1 proton. Sulfur has an atomic number of 16 which means that it has 16 protons. Carbon = _______ p+ Sodium = _______ p+ It is the number of protons which makes one element different from another. Atoms Atomic Mass - the average mass of the atoms of an element including all isotopes. To calculate the number of neutrons, take the atomic mass and subtract the protons. Neutrons = atomic mass – protons Nitrogen = 14 – 7 protons = 7 neutrons Fluorine = 19 – 9 protons = 10 neutrons Helium = 4 Oxygen =16 - Atoms Mass Number – the total number of protons and neutrons in an atom. Mass = neutrons + protons Oxygen = 8 protons + 8 neutrons = 16 Oxygen = 8 protons + 9 neutrons = 17 These different masses are the isotopes of oxygen. Practice Try #2 & 3 (p. 8) on your own. When done-Read the bottom of page 7 from Science 20 on electrical characteristics. Sketching Diagrams of Atoms Niel Bohr developed the idea that only a certain number of electrons are able to occupy an energy level. An energy level is a specific region surrounding the nucleus that is available for electrons. Level 1 Level 2 Sketching Diagrams of Atoms Step 1: Use the atomic number and atomic mass listed on the periodic table to determine the number of protons, electrons, and neutrons (PEN) that make up the atom. Step 2: Draw the nucleus of the atom with the appropriate number of protons and neutrons within the nucleus. Step 3: Use dots to represent the electrons in each energy level that surrounds the nucleus. Sketching Diagrams of Atoms Each energy level holds a specific # of e-. The number of electrons in a given energy level is shown by the number of elements in each period (row) on the periodic table. Sketching Diagrams of Atoms E.g.,. The first energy level can hold two electrons. This is shown by the first period having only two elements (H and He). The second energy level can hold eight electrons. This is shown by the second period of the periodic table having eight elements: Li, Be, B, C, N, O, F, and Ne. Bohr Diagram of Chlorine Atom Step 1: Determine the number of protons, electrons, and neutrons. P: number of protons = atomic number = 17 E: number of electrons = number of protons (b/c it is an atom) = 17 N: number of neutrons = atomic mass – number of protons = 35.45 – 17 = 18 rounded Bohr Diagram of Chlorine Atom Step 2: Draw the nucleus of the atom. The nucleus of the atom contains the protons and neutrons. 17p 18n Bohr Diagram of Chlorine Atom Step 3: Draw the electrons in their appropriate energy levels. Chlorine has 17 electrons. The first energy level can hold 2 electrons, leaving 15 more to place. The second energy level can hold 8 electrons, leaving 7 more to place. The third energy level can hold 8 electrons, but there are only 7 remaining. The final 7 will fit on the third energy level. Bohr Diagram of Chlorine Atom Bohr Diagram of Chlorine Atom Here is a more concise way to represent the final Bohr diagram 7e8e2e17p 18n Practice Try #5 a, d, & g (p. 9 of textbook) Lewis Dot Diagrams Is a representation of an atom that shows only the valence electrons. Valence electrons are the electrons in the outermost (last) energy level. Lewis Dot Diagrams Lewis Dot Diagrams Step 1: Write the chemical symbol. This symbol will represent the inner electrons and the nucleus. Step 2: Determine the number of electrons in the outermost energy level. (The column number will help you to do this). Step 3: Use a dot to represent each electron in the outer energy level. The dots are placed on the north, east, south, or west sides of the symbol. Each position only has room for two electrons. Double up on electrons only after all the other positions contain at least one electron. Lewis Dot Diagrams Atom Oxygen Bohr Diagram Lewis Dot Diagram Lewis Dot Diagrams Atom Oxygen Bohr Diagram Lewis Dot Diagram 8p 8n O Lewis Dot Diagram for Oxygen Lewis Dot Diagrams Atom Bohr Diagram Lewis Dot Diagram P Phosphorus 15p 16n Lewis Dot Diagram Practice Try #6c & d (p. 10) on your own. Octet Rule • All atoms strive to complete the outer shell with electrons and thus become a stable atom. They can complete these outer shells by gaining, losing or sharing electrons from other atoms. Gaining Electrons • Chlorine has 7 electrons in the outer shell & will gain ___ electron to complete the shell. • Since it has gained ___ electron, it now has a 1- charge and is now a charged atom called an ion. • Ion – an electrically charged atom or group of atoms. A negatively charged ion is called an anion. Losing Electrons • Sodium has 1 electron in its outer shell and will lose this electron to complete the outer shell. • Since it has lost an electron, it now has 1+ charge and is now a charged atom called an ion. • A positively charged ion is called a cation. If an atom gains electrons, it becomes negatively charged. If it loses electrons it becomes positively charged. The Periodic Table Metals vs. Non-Metals Metals tend to form positively-charged ions (cations) Non-metals tend to form negativelycharged ions (anions) Assignment Pg. 5 & 6 of workbook. Assignment Page 8 practice # 1 Page 9 practice #5 Page 10 practice #6 Answers Page 8 practice # 1 - 3 #1 a) Protons are found in the nucleus and have a positive charge. The # of protons is the same as the atomic number. b) Neutrons are found inside the nucleus and have no charge. They add mass to the atom. c) Electrons are found surrounding the nucleus and have a negative charge. They play a role in bonding. # 2 & 3 are in the back of the textbook Answers a) Carbon b) Hydrogen c) Aluminium Pg. 9 # 5 Answers d) lithium e) sodium f) fluorine Pg. 9 # 5 Answers Pg. 9 # 5 g) neon h) helium Pg. 10 #6 is in the back of the textbook