Writing Lewis Formulas Limitations of the Octet Rule

we see the octet rule is obeyed in hoth NH3 and. The sum of the formal 

This bookkeeping system helps us to choose among various Lewis formulas for a molecule or ion, according to the following guidelines. 

Now let s write some Lewis formulas for, and assign formal charges to, the atoms in nitrosyl chloride, NOCl, a compound often used in organic synthesis. The Cl atom and the O atom are both bonded to the N atom. Two Lewis formulas that satisfy the octet rule are 

A quick way to calculate formal charges for C, N, O, or F (and that generally holds for Cl, Br, and I as well) is to note the number of covalent bonds to that atom when it has an octet of electrons. The normal numbers of covalent bonds are C = 4, N = 3, 0 = 2, and F = 1. For each bond that exceeds the normal number of covalent bonds, add a formal positive charge to that atom. For each atom that has fewer covalent bonds, add a formal negative charge for each missing covalent bond. 

Each atom has an octet of electrons. The C atom, however, has only three covalent bonds, one fewer than usual, so it is assigned a formal charge of — 1. The O atom has three covalent bonds when it normally should have only two, so it is assigned a formal charge of -I-1. 

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WRITING LEWIS FORMULAS LIMITATIONS OF THE OCTET RULE... 

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