Chapter6

# Of shared 1 assign bonding electrons as one shared

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Unformatted text preview: hydrogen, eight for the own elements from carbon on in the periodic table). elements 1. Subtract the number in step 1 from the number in step 2. This is the number Subtract of shared (or bonding) electrons present (S = ). of shared ). 1. Assign bonding electrons (as one shared pair) to each connection Assign between two atoms in the molecule or ion. between 12/04/09 Zumdahl Chapter 13 29 Drawing Lewis Structures (con’t) 1. If any of the electrons earmarked for sharing remain, assign them in pairs If by making some of the bonds double or triple bonds. In some cases, there double may be more than one way to do this. Typically, double or triple bonds form only between atoms of carbon, nitrogen, oxygen, and sulfur. carbon nitrogen oxygen and sulfur 1. Assign the remaining electrons ( 1. octets to all atoms except hydrogen. ) as lone pairs to the atoms, giving lone 1. Determine the (C) on each atom, and write it next to that atom. 1. Determine on Check that the formal charges add to give a correct total charge on the molecule or molecular ion. molecule C ≡ group no. − no. of lone pair electrons − ½ (no. of electrons in bonding pairs) When choosing between more than one possible Lewis structure, the one When with the is usually preferred. with 12/04/09 Zumdahl Chapter 13 30 4 Lewis Structure of Methane (CH ) 1. Count up the total number of valence electrons available (A) by Count total available by first adding the group numbers of all the atoms present. If the species is a negative ion, add the absolute value of the total add charge; if it is a positive ion, subtract it. subtract H H C H H H H C H H 12/04/09 Zumdahl Chapter 13 31 1. Calculate the total number of electrons needed (N) for each atom Calculate total needed for to have its own noble-gas set of electrons around it (two for own hydrogen, eight for the elements from carbon on in the periodic table). table). H H C H H H H C H H 12/04/09 Zumdahl Chapter 13 32 1. Subtract the number in step 1 from the number in step 2. This Subtract is the number of shared (or bonding) electrons present (S). shared H H C H H N−A = H H C H H 12/04/09 Zumdahl Chapter 13 33 1. Assign two bonding electrons (as one shared pair) to each Assign two connection between two atoms in the molecule or ion. connection H H C H H 2 2 2 2 All bonding electrons assigned 12/04/09 Zumdahl Chapter 13 34 2 4 1. Count up the total number of valence electrons available (A) by Count total available by first adding the group numbers of all the atoms present. If the species is a negative ion, add the absolute value of the total add charge; if it is a positive ion, subtract it. subtract H C H H Lewis Structure of Ethylene (C H ) H C H H C H C H 12/04/09 Zumdahl Chapter 13 35 1. Calculate the total number of electrons needed (N) for each atom Calculate total needed for to have its own noble-gas set of electrons around it (two for own hydrogen, eight for the elements from carbon on in the periodic table). table). H C H H H C H H C H C H 12/04/09 Zumdahl Chapter 13 36 1. Subtract the number in step 1 from...
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