CHEM 012 7

CHEM 012 7

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Unformatted text preview: an only hold 2 electrons) •  When Cl gains an electron, it goes from a valence shell with 7 electrons to a valence shell of 8 electrons. •  The situaCon with Na is a liele different… 4 9/29/11 Sodium •  A Na atom only has one electron in its outer shell. •  When it loses the one valence electron, what happens? •  Instead of a total of 11 electrons, Na now has 10 electrons, which gives it the same electronic structure as Ne, which has an octet. •  Some textbooks will say that atoms are striving for a “noble gas configuraCon” How do bonds form? •  There are two main types of bonds that we will consider –  Ionic: transfer of one or more electrons from one atom to another. The ionic “bond” is formed by electrostaCc forces between oppositely charged ions. –  Covalent: sharing of one or more pairs of electrons between atoms to form a bond •  The molecules discussed in class so far contain covalent bonds •  Ionic bonds will be important in the chapter on water (Ch. 13) 5 9/29/11 Covalent Bonds •  Suppose we wish to form a covalent bond between H and F. –  H has one valence electron (wants 2) –  F has 7 valence electrons (wants 8) F H FH If each atom “shares” an electron with the other atom, each atom’s valence requirements (8 for F, 2 for H) are met. A pair of shared electrons is a covalent bond Covalent Bonds •  Once the bond is formed, the electrons lose their “idenCty”, i.e. it is impossible to tell which electrons originated from F and which from H. •  Thus, we would usually write the Lewis structure like this: FH •  Finally, co...
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This note was uploaded on 09/06/2012 for the course CHEM 012 taught by Professor M.lester during the Fall '12 term at UPenn.

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