CHEM 1A03 Study Guide - Final Guide: Bond Order, Formal Charge, Bond Length

• School: McMaster University
• Department: Chemistry
• Course: CHEM 1A03
• Professor: David J.H.Emslie

Document Summary

For this ion, there are 4 equivalent charge-minimized structures, there are known as. True structure of phosphate is average of all four structures. To get average formal charge (on oxygen in this case), we sum the charges on all oxygen atoms that the double bonds resonate in-between and divide it by that same number of oxygen atoms. Take total number of bonds between central atom and atoms that double bond is resonating between, divide it by total number of places where the bonds are found. So(cid:373)eti(cid:373)es, we (cid:272)a(cid:374)"t reso(cid:374)ate arou(cid:374)d to all o(cid:454)(cid:455)ge(cid:374) ato(cid:373)s. Resonance structures, only electrons move, never atoms. When we calculate average formal charge on the other oxygen atoms, there are two negative charges and they only move around these three oxygen atoms, (so formal charge is -2/3) When we look at average bond order, single bond plus single bond plus a double bond, so 4 total bonds resonating in 3 places, average bond order is 4/3.