The Construction of structures for molecules and poly atomic ions : The below written method is applicable to the species in which the octet rule is not violated.

         (i) To determine the total number of valence electrons in all atoms present, including the net charge on the species (n₁).

         (ii) To determine n₂ = [2 × (number of H atoms) + 8 × (number of other atoms)].

 

        (iii) Determine the number of bonding electrons, n₃, which equals n₂ - n₁. No. of bonds equals n₃/2.

         (iv) Determine the number of non-bonding electrons, n₄, which equals n₁ - n₃. No. of lone pairs equals n₄/2.

         (v)          Knowing the central atom (you'll need to know some chemistry at this point, as math will not help hear!), arrange and distribute other atoms and n₃/2 bonds. Then the complete octets making use of the n₄/2 lone pairs.

         (vi) Establish the 'formal charge' on each atom.

         (vii) The Formal Charge = [valence electrons present in the atom) - (number of bonds) - (number of unshared electrons)]

         (viii) Other aspects such as resonance and many athers can now be incorporated.

Illustrative examples

         (i)  [2 added for net charge]

             n₂ = (2 × 0) + (8 × 4) = 32 (no. H atom, 4 other atoms (1'C' and 3 'O')

             n₃ =  32 - 24 = 8, hence 8/2 = 4 bonds

             n₄ = 24 - 8 = 16, hence 8 lone pairs.

Since carbon is the central atom, 3 oxygen atoms are to be arranged around it, thus, , but total bonds are equal to           4.

         Hence, we get     . Now, arrange lone pairs to complete octet     

         (ii)  n₁ = 4 + (6 × 2 ) = 16

          n₂ = (2 × 0) + (8 × 3) = 24

          n₃ = 24 - 16 = 8, hence 4 bonds

         n₄ = 16 - 8 = 8, hence 4 lone-pairs

         Since C is the central atom hear, the two oxygen atoms are around to be arranged it hence the structure would be;  O - C - O, but total no. of bonds = 4

            Thus,  O = C = O.  After arrangement of lone pairs to complete octets, we get,   and hence final structure is 

Email based Chemistry assignment help - homework help at Expertsmind

Are you searching chemistry expert for help with Polyatomic ions questions?  Polyatomic ions topic is not easier to learn without external help?  We at www.expertsmind.com offer finest service of Chemistry assignment help and chemistry homework help. Live tutors are available for 24x7 hours helping students in their Polyatomic ions related problems. We provide step by step Polyatomic ions question's answers with 100% plagiarism free content. We prepare quality content and notes for Polyatomic ions topic under chemistry theory and study material. These are avail for subscribed users and they can get advantages anytime.

Why Expertsmind for assignment help

1. Higher degree holder and experienced experts network
2. Punctuality and responsibility of work
3. Quality solution with 100% plagiarism free answers
4. Time on Delivery
5. Privacy of information and details
6. Excellence in solving chemistry queries in excels and word format.
7. Best tutoring assistance 24x7 hours