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what is a good step by step approach to learning lewis dot structure?

studyong for chem test

Right…. Just put dots around them then share them until each has 8 of them.

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2 Responses to “what is a good step by step approach to learning lewis dot structure?”

  1. dynam1c Says:
    November 16th, 2009 at 4:37 am

    I Actually Teach Chemistry 212 (lab) @ Northern Illinois University, So bare with me because i promise this will pay off but lewis dot structures are a very visual explanation…

    1. Count up the number of valence electrons on the atoms of the molecule, (eg. C= 4 O= 6 N=5, F=7) add them all up (be sure to look for coefficients like H20 has two H so that would be 2 electrons) also look for charge on the molecule if it’s (-) add 1 electron, if + subtract 1.

    2. Draw a basic stick structure connecting the central atom (more on central atoms in a moment) just draw a single bond between the central atom and the other element connected to it. now count the number of electrons used in these bonds (2 electrons for each bond). Now subtract that number from your total electrons (ex. (H2O) has14 electrons…you should have just draw two single bonds meaning 14-4=10 electrons remaining.) (quickly central atoms are generally the first atom lists in a compound formula CH4 = carbon is central…hydrogen is NEVER the central atom (and can only form 1 single bond never a double bond (it has now p orbital)) ok common central atoms are C, S, N, B and the element below them in periodic table. (if C and another element are in same compound then C is central…ex HCN-)

    3.Finally start adding the electrons remaining around the constituent atoms in pairs until each you’ve added 6 then move to the next. (note the 6 + 2 electrons from the bond makes a stable 8)

    4. ok if there are more electrons left add them to the central atom

    5. if there are no more electrons and the central atom has 8 electrons( bondscount for 2 e-) your done, if the central atom has less than 8 then you need to make double bonds until it has eight to do this remove one lone pair from a constituent and then draw a second bond between the central atom and the constituent atom. the most common double bonds are O, S, N though others may exist usually oxygen doubles before other element so if you have a choice choose O…also N can some times for a triple bond two ex. are N2 and HCN- google these lewis structures to see what i mean.

    6. you should be done now just double check all you atoms have 8 electrons around it. (note there are special case where the cetral atom can have more the 8 ex SF6, and BH3 only has 6 e on B because H can’t double bond.

    good luck hope this helps and wasn’t to horribly long and confusing
    References :
    ME

  2. icecreamboy121 Says:
    November 16th, 2009 at 5:26 am

    Right…. Just put dots around them then share them until each has 8 of them.
    References :

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