Lewis Structures (Oxygen)

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Regina Chi 2K
Posts: 51
Joined: Fri Sep 26, 2014 2:02 pm

Lewis Structures (Oxygen)

Postby Regina Chi 2K » Mon Oct 27, 2014 5:34 pm

Hi! I have a question regarding the Lewis structure of molecules that have oxygen. Why is it that in some situations, oxygen double bonds and in some others, it has only a single bond? I know that oxygen tends to have double bonds to complete the octet, but for example, why is oxygen single bonded to sulfur in (SO3)2-??? Does it only have to do with better formal charge? And how can we gauge beforehand what generally oxygen will be bonded as? Thanks in advance! :)

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: Lewis Structures (Oxygen)

Postby martha-1I » Mon Oct 27, 2014 5:40 pm

Oxygen tends to like to have double bonds because when drawing the lewis structure we want to form the most stable structure. This means that although it is not wrong for it to have a single bond, in some cases, a single bonds gives the overall structure a positive or negative charge and we want the most stable lewis structure which is the structure that has the most zeros as its formal charge.

martha-1I
Posts: 76
Joined: Fri Sep 26, 2014 2:02 pm

Re: Lewis Structures (Oxygen)

Postby martha-1I » Mon Oct 27, 2014 6:01 pm

I am not familiar with a way to figure out what type of bond Oxygen will have before starting the Lewis Structure. When drawing the Lewis Structure I recommend to 1) first count the valence electrons of the molecule, 2) then determine what is the central atom for that molecule by determining which atom has the lowest ionization energy. 3) After, draw the Lewis Structure and if the total number of valence electrons add up to the initial number of valence electrons (number from step 1) then you are done and you could then check the formal charge to see if the Structure you drew is the most stable. If the number of valence electrons from the Lewis Structure goes over the initial number of valence electrons then make a double or triple bond where needed. Lastly, check the formal charge to make sure that it is at its most stable (it has the most formal charges that equal zero).
Hope this helps!


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