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Chapter 6 State Standards: 3.a; 7.b 1Contreras
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The Atom 2Contreras
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There have been many changes that have contributed to what the atomic theory is today Over centuries many scientist have discovered and clarified information about the atom 3Contreras
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The atom is the smallest particle within an element An element is made-up of MANY atoms that are exactly the same Atoms cannot be seen with the naked eye 4 It would take 106 million billion Au atoms to cover the surface of a dollar bill 70 million He atoms could fit on your pencil eraser Contreras
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Nucleus – small, dense, positively charged center Protons – positively charged particles in the nucleus Neutrons – particles in the nucleus with no charge Electrons – negatively charged particles found in electron clouds outside the nucleus. Determines size of atom. 5Contreras
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6 Electron Cloud Contreras
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Protons 1 amu Positively charged (+) Neutron 1 amu No charge The nucleus is the biggest part of the atom 1 amu = 0.0000000000000000000000017 g Atomic Mass Unit (amu ) 7 If there was a nucleus the size of a grape, it would have a mass of 9 million metric tons (18 million pounds)! Contreras
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Electrons Negatively charged (-) Found only in electron clouds Smallest mass particle of the atom 1/1800 size of proton and neutron Electron Cloud Region outside the nucleus where electrons are contained 8Contreras
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Atoms and Elements 9Contreras
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1. Gravitational Force – holds all the parts of the atom together 2. Electromagnetic Force – attracts electrons (-) around nucleus (+) 3. Strong Force – holds protons in nucleus together 4. Weak Force – holds nucleus together in radioactive atoms 10Contreras
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Nucleus has a positive charge (because of protons) Electrons have negative charge For an atom to have no charge, positive and negative charges need to be balanced (# of protons and electrons is equal) An ion is an atom with a charge Positively charged ion = atom has lost 1+ electron(s) Negatively charged ion = atom has gained 1+ electron(s) 11Contreras
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Atomic number - # of protons in nucleus Atomic number (# of protons) is the same for all atoms of a certain element Atomic number tells you what element it is! Atomic mass (mass number) = protons + neutrons Atomic mass needs to be rounded 12 Atomic mass Contreras
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Electron Cloud Maximum # of Electrons 12 28 318 432 13Contreras
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An element’s atomic number tells where it is on the periodic table Atomic number = # protons (+) # protons (+) = # electrons (-) As long as the atom is not an ion Atomic mass = protons + neutrons 14Contreras
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Isotopes 15Contreras
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Atoms of the same element that have different number of neutrons in their nucleus Isotopes still have same: Atomic number # protons # electrons Different # neutrons Named according to the mass number hydrogen-1 and hydrogen-2 16Contreras
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Hydrogen has an atomic number of 1 So Hydrogen has 1 proton Hydrogen has 2 additional isotopes (H with different number of neutrons) Deuterium (1 proton & 1 neutron) Tritium (1 proton & 2 neutrons) 17Contreras
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18 To find the number of neutrons: Protons + neutrons = mass number Mass number – atomic number (# proton) = neutrons Mass numberof Carbon is 12 Mass number: 12 Atomic number: - 6 # Neutrons: ~6 Contreras
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An unstable atom where the nucleus will change and eventually fall apart over time Will give off energy when they fall apart Ex. Radon; Uranium Found in nature No stable isotope exists 19 http://computershopper.com/shoptalk/Radioact ive_Man_Number_One_v_1024.jpg Contreras
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Ions have a charge Positive charge if lost an electron ▪ K 1+ has lost an electron Negative charge if gained an electron ▪ Cl 2- has gained two electrons Isotopes Have same number of protons & electrons, different number of neutrons 20Contreras
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NameLocationCharge NucleusCenter of atomPositive ProtonNucleusPositive NeutronNucleusNone ElectronElectron cloudNegative electron proton/neutron nucleus atom element smallest mass biggest mass 21Contreras
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