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