Can someone please help me with the resonance structure for AlCl3. When I draw it, the central Al does not have a complete octet. I read that this is usually the case for atoms like Boron and Aluminium who only have three valence electrons. Is this correct? Also, as a follow on question, does AlCl3 display resonance?
Since aluminum only has 3 valence electrons it will be missing two electrons from its octet. This means that one of the chloride groups must share an extra electron group with the aluminum. Any three of the chlorides can share an extra electron pair with it (i.e. they'll have 2 lines attached to aluminum), so there is resonance. There are 3 to be specific, one for each chloride sharing another electron pair with Al.
I'll do NO2- as an example. The Lewis structure is O=N-O with two electron pairs on the left O and 3 electron pairs on the right O and one electron pair on the N. But you could also draw it as O-N=O. So, those are the two resonance structures. The actual is where N has 1.5 bonds to each O on average.
