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The Atom Quick! Time yourself writing the numbers from 1000-1050. Then, multiply the time by 20,000 How small is an atom? A human hair is about 1 million atoms across And… a million is a lot! It would take you at least 20 days without sleeping (at just over 1-second per number) to count to 1,000,000 out loud. 50 million (all the people in Oregon x 12.5 or almost twice the number of people in California) atoms lined up = 1 cm. In other words, if all of the people in Oregon were atoms & they lined up holding hands, the line would be less than 1mm long If each atom in a single marble were the same size as a grain of sand, you would end up with enough sand to cover the whole of Oregon with a layer close to a thousand feet (2/3 or a mile) thick. If you walked around the equator of the earth continually without stopping to sleep or eat, it would take about 12,500 hours or 520 days. It's a big place! If a golf ball could be magnified to the size of the whole earth, most of its atoms would be more or less the size of a golf ball Atomic Structure Parts of an Atom Proton • +1 charge • In nucleus only • Mass= 1amu (1.6 x 10-24g) Neutron • 0 charge • In nucleus Electron • -1 charge • Around only • Mass= 1amu (1.6 x 10-24g) • nucleus- in shells Mass= 9.1 x 10-34g (relatively insignificant) Electrons But… Electrons take up by far the most space, 10,000 times more than the nucleus Nucleus = basketball then electrons stretch out in a diameter of 7.5km (all the way to Phil’s Trails, Target, Elk Meadow School- almost) Nucleus= marble then electrons stretch 100m (size of a football field) Atomic Structure Atomic Number = # of protons and # of electrons Mass number = # of protons + neutrons Try these… I have an atomic number of 13 • Aluminum I have an atomic mass of 32 • Sulfur I have 83 electrons • Bismuth Number of neutrons in Cobalt (Co) • 32 Have 10 neutrons • Neon AND Fluorine But wait! How many neutrons does Chlorine have? 18.5? Isotopes= atoms with the same # of protons, but different # of neutrons (and thus different mass) • Ex: sodium-23, sodium-24 • Symbol: Mass Radioisotopes Unstable isotopes= radioactive= radioisotopes • Carbon-14 decays into carbon-12 over time by kicking off neutrons (or parts of neutrons) Have many uses! • Americium-241= smoke detectors • Technetium-99= thickness gauges Back to Chlorine…. Atomic Mass on the periodic table is a weighted average of the atomic masses of all isotopes (see p.119) Average Atomic Mass = (% of isotope 1)(mass of isotope 1) + (%of isotope 2)(mass of isotope 2) +… Chlorine = 75.77%(35) + 24.33%(37) = 35.5 amu So… What is the most common isotope of Hydrogen? Hydrogen-1 How about Zinc? Zinc-65 Nope Is this the most common Li isotope? Carbon is 98.89% carbon-12 and 1.11% carbon-13. What’s the average atomic mass? 98.89%(12) + 1.11%(13) = 12.011 amu A couple more… What’s the most common isotope of Gallium-70 gallium? If element X is 57% X-25, 29% X-26 and 14% X-27, what’s the average atomic mass of X? 57%(25) + 29%(26) + 14%(27) = 25.57 amu