Wi10-Lec3 - Lecture 3 1/12/10 Atoms, Molecules and Bonds...

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1 Lecture 3 1/12/10 Atoms, Molecules and Bonds Atoms, Molecules and Macromolecules…oh my!
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2 What are Atoms?
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3 e - p + n n e - p + p + e - atomic nucleus (a) Hydrogen (H) (b) Helium (He) The simplest atomic structures
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4 Electron shells • Electrons orbit around the nucleus at specific distances • called electron shells. Different atoms have different electron shells: Shell #1 holds two electrons Shells #2 and up hold up to eight electrons
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5 Carbon (C) Oxygen (O) Phosphorus (P) Calcium (Ca) O C P Ca 8 e - 8 e - 2 e - 20 p + 20 n 2 e - 4 e - 6 e - 2 e - 2 e - 6 p + 8 p + 6 n 8 n 5 e - 8 e - 2 e - 15 p + 16 n The first four atomic electron shells Ok…how does this relate to what goes on in my cells?
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6 Atoms interact to form Molecules Molecules make up everything in your cells!!! How Atoms Interact All atoms want a “full” outer electron shell Inert atom —has a full outer shell—won’t react with other atoms (ex: Noble gasses—Neon, etc) Reactive atom —partially full outer shell—reacts with other atoms to fill it (ex: carbon, nitrogen, sodium)
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7 Molecules Two or more atoms held together by bonds between electrons in their outer electron shells Bonds: eHarmony for atoms • Reactive atoms combine to fill their outer electron shells • 3 main types of bonds formed Ionic Covalent Hydrogen
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8 Ionic Bonds– “giving it away for free” 1 electron is passed from one atom to another • One partner becomes positive, the other negative, and then they attract one another. •Na + + Cl becomes NaCl (sodium chloride) Fig. 2-5 Electron transferred Attraction between opposite charges Sodium ion (+) Chloride ion (–) Sodium atom (neutral) Chlorine atom (neutral) 11 p + 11 n 17 p + 18 n 11 p + 11 n 17 p + 18 n Na + Cl - Cl - Na + Cl - Cl - Na + Na + Cl - Neutral atoms (a) An ionic compound: NaCl (c) Ions (b) Covalent Bonds—“Electron Sharing” Bonds between two atoms that share electrons in their outer electron shell
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9 2 types of Covalent Bonds Non-polar: atoms equally share electrons Nonpolar covalent bonding in hydrogen (uncharged) Electrons spend equal time near each nucleus
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This note was uploaded on 03/11/2010 for the course BILD BILD 10 taught by Professor Jenniebever during the Spring '09 term at UCSD.

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Wi10-Lec3 - Lecture 3 1/12/10 Atoms, Molecules and Bonds...

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