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Atomic Structure Chemistry: Chapter 4 Atoms •Building block of matter •Cannot be seen •Known to exist through indirect evidence. Gathering information w/o actually seeing or touching the object. Used to develop a mental picture or model. Ex. gravity History of the atom overview http://www.nobeliefs.com/atom.htm http://www.chalkbored.com/lessons/chemistry-11/atomic-models-handout.pdf Greek Model •2400 years ago, Greek philosopher Democritus •1st to use the term “atom” meaning “indivisible” or “not to be cut” •Ancient Greeks believed matter was made of 4 basic elements: fire, air, water, and earth Dalton’s Model •Early 1800’s, English chemist, John Dalton •Meteorologist •Developed the atomic theory 1.All elements are composed of atoms. 2.Atoms of the same element are identical. 3.Atoms of different elements are different. 4.Compounds are formed by joining 2 or more atoms. Thomson’s•1897 •Proved atoms were made up Model of even smaller particles •Discovered corpuscles electrons •Model called “plum pudding” Rutherford’s •1908 Model •Discovered that atoms have dense, positively charged nucleus •Fired charged particles at gold foil, some went through while others were deflected. Subatomic •Protons particles Positively charged; +1 In the nucleus Distinguishing Characteristics: • Mass • Charge • Location •Neutrons No charge In the nucleus •Electrons Negative charge; -1 Outside the nucleus Atomic Number Mass Number or Atomic mass •Number of p+ in the nucleus •Each element has a certain number of p+ •Also equal to the number of e•Sum of p+ and neutrons •Mass # = atomic # + neutrons 3 Li 7 Atomic # Chemical symbol Mass # Isotopes •Atoms of the same element •Have different number of neutrons, but the same number of protons & electrons •They have the same atomic #,but different mass # because of the # of neutrons •Ex. (O-16, O-17, and O-18) Each O has 8 protons, but the neutrons vary Bohr’s Model •1913 •Discovered that electrons move in energy levels (orbits) around the nucleus •Called the “solar system model” Summary of history of the atom http://www.aasd.k12.wi.us/west/science/b artel/Chemistry/Ch3/History%20of%20At om%20Notes.pdf http://www.footprintsscience.co.uk/atomicstructure1.htm Arrangement of electrons •Electrons are in energy levels within an electron cloud. Around the nucleus •1st energy level can hold •2nd energy level can hold •3rd energy level can hold •4th energy level can hold 2 e8 e18 e32 e- Each orbital can contain 2 electrons Electron Configuration •Arrangement of electrons in orbitals •Most stable in the lowest possible energy level •If all electrons have the lowest possible energies, the atom is in ground state •Ex. Magnesium Symbol Mg Atomic Number 12 # of p+ 12 # of e- 12 1st energy level ____ 2 (can hold 2) 2nd energy level ____ 8 (can hold 8) 3rd energy level ____ 2 (can hold 18) Magnesium 12p+ 12n0 •Ex. Aluminum Symbol Al Atomic Number 13 # of p+ 13 # of e- 13 1st energy level ____ 2 (can hold 2) 2nd energy level ____ 8 (can hold 8) 3rd energy level ____ 3 (can hold 18) Aluminum 13 p+ 14 n0 •Ex. Fluorine Symbol F Atomic Number 9 # of p+ 9 # of e- 9 1st energy level ____ 2 (can hold 2) 2nd energy level ____ 7 (can hold 8) 3rd energy level ____ none (can hold 18) Fluorine 9 p+ 10n0 Practice Determine the # of e- in the following elements. Draw their electron configuration. Lithium Nickel Oxygen Sulfur Helium Argon Titanium Carbon Beryllium Zinc Next Lab can be edible This lab you will be creating a Bohr Model of any atom that you choose beyond Oxygen You must bring your own supplies for this All parts of the atom MUST BE REPRESENTED EX: cookies with icing to hold the P+ N0 and E- in energy levels Preparing for Lab You will be having a lab where you concentrate on Atomic Structure Make a list of supplies that you will need in order to make a model of your atom Bring your supplies to class or drop them by room 604 that morning After you complete your model… Once you have completed your model you are to show it to me. You will need to make a key of what is representative of the protons, neutrons, and electrons. You are to draw a Bohr model on the same page. Make a key that show the atomic name, number, symbol and atomic mass number