For ions we must adjust the number of electrons available

# For ions we must adjust the number of electrons available -...

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For ions we must adjust the number of electrons available, A. Add one e - to A for each negative charge. Subtract one e - from A for each positive charge. The central atom in a molecule or polyatomic ion is determined by: The atom that requires the largest number of electrons to complete its octet goes in the center. For two atoms in the same periodic group, the less electronegative element goes in the center. Writing Lewis Formulas: The Octet Rule Example 7-2: Write Lewis dot and dash formulas for hydrogen cyanide, HCN. Writing Lewis Formulas: The Octet Rule Example 7-3: Write Lewis dot and dash formulas for the sulfite ion, SO 3 2- . You do it!
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Unformatted text preview: Resonance Example 7-4: Write Lewis dot and dash formulas for sulfur trioxide, SO 3 . You do it! Formal Charge Calculation of a formal charge on a molecule is a mechanism for determining correct Lewis structures The formal charge is the hypothetical charge on an atom in a molecule or polyatomic ion. The best Lewis structures will have formal charges on the atoms that are zero or nearly zero. Formal Charge Rules for Assigning Formal Charge 1. Formal Charge = grp number – (number of bonds + number of unshared e-) 2. An atom that has the same number of bonds as its periodic group number has a formal charge of 0....
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