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Lecture3a - Ionic bonding attraction between ions •...

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BIOLOGY 1001 Wednesday, January 23, 2008 Lecture 3 Building-Up Principle Electrons fill the shell closest to the nucleus, then begin to occupy the next shell. 1 st : 2 Electrons 2 nd : 8 Electrons 3 rd : 8 Electrons e.g., Atomic Number of Carbon (C) = 6 6 Electrons 2 in 1 st Shell 4 in 2 nd Shell Electron Shells p. 24 Isotopes Isotopes vary in number of neutrons. p. 23 Ions Atoms are most stable with the full outer shell. Extra Electrons: - Charge Fewer Electrons: + Charge Figure 2-3 p. 25 What determines whether Atoms will interact? Answer: The Number and arrangement of their electrons. p. 24 Bond is union between electrons in an outer shell of atoms. Atoms bond to form molecules. Molecules may obtain atoms only one element - O 2 Compounds contain more than one element – H 2 O
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Important Bonds in Biological Molecules Ionic Bonds, Covalent Bonds, and Hydrogen Bonds
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Unformatted text preview: Ionic bonding attraction between ions. • Sodium can lose 1 electron chlorine can gain 1 electron. • Sodium becomes a “+” ion. • Chlorine becomes a “-“ ion. Table 2-2, Figure 2-3, p. 25-26 Covalent Bonding: Atoms share electrons to fill outermost shell. • Single Covalent Bond 1 Pair Electrons • Double Covalent Bond 2 Pair Electrons • Triple Covalent Bond 3 Pair Electrons Figure 2-4, p. 26 Non-polar Covalent Bonds • Atoms share electrons equally. • Hydrogen Gas (H-H), Methane (CH 3 ) Figure 2-4, p.26 Polar Covalent Bonds • Electrons spend more time around one atom and less around another. Figure 2-4, p. 26 Hydrogen Bonds Polar molecules carry slight charges • Electrons favor one atom over another. • Hydrogen bond forms between “+” end of one molecule and “-” end of another. Figure 2-5, p. 28...
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Lecture3a - Ionic bonding attraction between ions •...

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