Lect_W5_151 WESO(short) - General Chemistry CHEM 151 Week 5...

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UA GenChem General Chemistry General Chemistry CHEM 151 CHEM 151 Week 5
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UA GenChem Week 5 Reading Assignment See D2L CONTENT
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UA GenChem Unit 2: Zooming I n Unit 2: Zooming I n What are they made of? What holds them together? Why are they joined in this way? Why are there forces between them? ( intermolecular forces ) They could be atoms, molecules, ions
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UA GenChem Electrical Nature Electrical Nature How do we explain this? We assume atoms and molecules have an electrical nature ( they are made of + and - charges ) Understanding “ charge distribution ” in atoms and molecules is of central importance in chemistry.
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UA GenChem PLANETARY MODEL α
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UA GenChem PLUM PUDDING MODEL . α What experiment Resolved the problem?
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UA GenChem Rutherford and Marsden
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UA GenChem Current view of the atom X 1 2 4 3 1)Atomic number(Z) = # protons = # electrons= ? 11 23 1+ 3 1) Mass number (A) protons plus neutrons neutrons = Na 3) Ionic charge -- 0 if neutral atom + if electrons lost - if electrons added Electrons? 4) Number of times previous item appears in the compound . Na 3 ?
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UA GenChem How many electrons in 16 S 2- ? 1. 14 2. 16 3. 18 4. Can’t tell 5. Choice Five
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UA GenChem Some samples 19 1- F 9 p = e = n = 235 U 92 p = e = n =
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UA GenChem objective Given any element or ion find the Number of protons neutrons electrons (especially ions) p= n= e= + 3 27 13 Al
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UA GenChem Atoms are characterized by the number of protons in the nucleus ( atomic number, Z ). I n a neutral atom , the number of protons is equal to the number of electrons. Mass Number, A (protons+ neutrons) Atoms Atoms Made of electrons ( - ) , protons ( + ), and neutrons (no charge). old ne w X A Z O 16 8
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UA GenChem Atomic Number, Atomic Number, Z Z , and , and Mass Number, Mass Number, A A Mass Number Mass Number A A = # protons + # neutrons = # protons + # neutrons A boron atom can have A boron atom can have A A = 5 p + 5 n = 5 p + 5 n A Z 10 5 B All atoms of the same element have the same All atoms of the same element have the same number of protons number of protons in the nucleus, in the nucleus, Z, Z, b but they may differ in the number of neutrons
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UA GenChem Dalton’s model revisited All matter is made of atoms (Greeks) All atoms of an element are the same Compounds are whole number combinations of different atoms In a chemical Rx. Atoms are reorganized but never made or destroyed By all experiments Cl (chlorine) weights 35.45 amu You CANNOT HAVE 0.45 of a mass unit DALTON’s LAW was in trouble
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UA GenChem I sotopes I sotopes Atoms of the same element ( Atoms of the same element ( same Z same Z ) but ) but different mass number ( different mass number ( A A ). ). Boron-10 ( Boron-10 ( 10 10 B) has B) has 5 p 5 p and and 5 n 5 n Boron-11 ( Boron-11 ( 11 11 B) has B) has 5 p 5 p and and 6 n 6 n 10 B 11 B How many p and n in this atom? C 12 6 ?? 208 82 What is this?
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UA GenChem What is the nuclide symbol for plutonium-246? How many protons, neutrons and electrons are in the isotope?
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