Lect_W5_151 WESO(short) - UA GenChem General Chemistry...

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Unformatted text preview: UA GenChem General Chemistry General Chemistry CHEM 151 CHEM 151 Week 5 UA GenChem Week 5 Reading Assignment See D2L CON TEN T UA GenChem Unit 2: Zooming I n Unit 2: Zooming I n What ar e they made of? What holds them together ? Why ar e they joined in this way? Why ar e ther e for ces between them? ( inter molecular for ces ) They could be atoms, molecules, ions UA GenChem Electr ical N atur e Electr ical N atur e H ow do we explain this? We assume atoms and molecules have an electr ical natur e ( they ar e made of + and - char ges ) Under standing char ge distr ibution in atoms and molecules is of centr al impor tance in chemistr y. UA GenChem PLANETARY MODEL UA GenChem PLUM PUDDING MODEL . What experiment Resolved the problem? UA GenChem Rutherford and Marsden 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 ? UA GenChem How many electrons in 16 S 2- ? 1. 14 2. 16 3. 18 4. Cant tell 5. Choice Five UA GenChem Some samples 19 1- F 9 p = e = n = 235 U 92 p = e = n = UA GenChem objective Given any element or ion find the Number of protons neutrons electrons (especially ions) p= n= e= + 3 27 13 Al UA GenChem Atoms ar e char acter ized by the number of pr otons in the nucleus ( atomic number , Z ). I n a neutr al atom , the number of pr otons is equal to the number of electr ons. Mass N umber , A (pr otons+ neutr ons) Atoms Atoms Made of electr ons (- ) , pr otons ( + ), and neutr ons (no char ge). old ne w X A Z O 16 8 UA GenChem Atomic N umber , Atomic N umber , Z Z , and , and Mass N umber , Mass N umber , 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 pr otons number of pr otons in the nucleus, in the nucleus, Z, Z, b but they may differ in the number of neutr ons UA GenChem Daltons 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 DALTONs LAW was in trouble 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 )....
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This note was uploaded on 03/30/2009 for the course CHEM 151 taught by Professor Staff during the Fall '08 term at University of Arizona- Tucson.

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Lect_W5_151 WESO(short) - UA GenChem General Chemistry...

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