[MIA6]

1. For which of the following molecules can two equivalent resonance structures be drawn: O3, C6H6(benzene), N2O, and [N3]-?
What does it mean by two equivalent resonance structures?? does it mean that single, single bonds, or double,double bonds? instead of one single, one double bond?
O3 has a double bond and single bond, benzene has double bonds and single bonds, N2O has one single and one double bond, and N3-has all single bonds.
2. Why the structure of CO is triple bonds? I think double bonds are better, no formal charges.

Thanks. 

[AWK]

start from:
http://en.wikipedia.org/wiki/Resonance_(chemistry)