Ch_322a_1.04

Ch_322a_1.04 - H N 1-1 5-(3+2) Examples of Formal Charges...

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Formal Charge It is possible to assign positive and negative charges to atoms in Lewis structures. These formal charges often give insight into chemical reactivity. The sum of all the formal charges must equal the total charge (if any) on the Lewis structure. The formal charge on an atom is obtained by subtracting the number of valence electrons that "belong" to the atom in its bonded state from the number of valence electrons in the neutral free atom . Assignment of Valence Electrons in the Bonded State (1) Electrons in covalent bonds are shared equally by the two atoms held together by the bond. (2) Nonbonding electrons are assigned completely to the atom where they are located. The total number of valence electrons assigned to an atom in its bonded state is one half the number of electrons in covalent bonds plus all the nonbonding electrons.
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Examples of Formal Charges CH 4 :C: : H H H H atom valence electrons in: free atom bonded state H C formal charge 1 - 1 0 4 - 4 0 NH 3 :N: H H H atom valence electrons in: free atom bonded state formal charge
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Unformatted text preview: H N 1-1 5-(3+2) Examples of Formal Charges NH 4 + :N: : H H H H atom valence electrons in: free atom bonded state formal charge H N 1-1 5-+1 4 CO 3 2-C :O: :: :O: :O: atom valence electrons in: free atom bonded state formal charge C O O 4-4 6-6 6-(6+1)-1 Table of Common Formal Charges Group Formal Charge +1-1 3 B Al B-Al-4 C + C C = C C :-5 + N N-N: 6 O + O:-O: 7 X + X: ( X = F, Cl, Br, I) X: :-Quiz 1.04 Assign the charge in the cyanide ion, CN-. solution: This is a 10 valence electron system. Draw a Lewis structure that follows the Octet Rule. C N : : Assign the charge.-Draw a correct Lewis structure for the hydrogen sulfite ion, HSO 3-. solution: This is a 26 valence electron system. Draw a structure with the S as the central atom. S O O O = : : : : : H This structure has 24 valence electrons. Where can we add the remaining two electrons? : Where is the formal charge?...
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_1.04 - H N 1-1 5-(3+2) Examples of Formal Charges...

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