Sketch the form of the \({ }^{19}\) F NMR spectrum and the \({ }^{11}\) B NMR spectrum of \({ }^{11} \mathrm{BF}_{4}^{-}\).

Text Transcription:

^19 F

^11 B

^11 BF_4^-

4.4 Exceptions to octet rule continued Example problems Draw the Lewis structure for SF₆ 1) S has 6, F has 7 and we have 6 Fs (7x6=42). Total we have 48 2) S is the least electronegative so it is the inner atom. 3) We have used 12 electrons so far. So, we have 36 left. S can have an expanded octet so it can have more than 4 bonds. 4) Now we have used all the electrons. Draw the Lewis structure for SO₂²⁻ 1) S has 6, O has 6 and we have 2 Os (6x2=12), and there is a -2 charge so we gain 2 electrons. Total we have 20. 2) S is the least electronegative so it is the inner atom. 3) We have used 4 electrons. So, we have 16 left. 4) Now all electrons have been used. 4.5 Resonance Resonance- when double or triple bonds can exist in multiple spaces The actual observed structure of ozone (O₃) is a hybrid of the above structure. Where both bonds are the same length and strength. The bonds end up being 1.5 bond. The electrons are delocalized leading to resonance stabilization. Bond order= number of bonds/ number of bonding positions Example problems Draw the resonance forms of NO₃⁻ and determine the bond order 1) First let’s draw the Lewis structure. This structure needs one more bond between the N and an O. Which mean the bond could be placed in three different spots. 2) Let’s draw all the resonance structures 3) For the bond order there are 4 bonds and 3 bonding positions. So the