Listed below are 25 molecules or ions grouped in seven groups of 3-5 each. Each group shares some common feature and, when that feature is considered, no other grouping of the molecules is correct. Your task is to determine that common feature.  I would suggest that you begin by applying VSEPR rules to predict the structures.  Don't use the rotatable models unless you have to.


1.    N2, UO22+, C2H2, NO2+    rotatable models


2.    HCl, COS, HCN, SCN-    rotatable models


3.    H2O, PF4-, cis-Pt(NH3)2Cl2, NO2-, cis-Co(NH3)4Cl2+    rotatable models


4.    NH3, CH3Cl, cis-Co(NH3)3Cl3    rotatable models


5.    PdCl42-, trans-Co(NH3)4Cl2+, XeF4    rotatable models


6.    CH4, CoCl42-, PF4+    rotatable models


7.    SF6, Co(NH3)63+, Cr(CO)6    rotatable models


Do the species HOCl, CO2, CH2Cl2, C6H6 and Co(NH3)5Cl2+ fit in any of these groups? If so, which ones?   rotatable models