posted by CHEM .
Which molecule or ion does not have a tetrahedral molecular geometry?
Can you draw the Lewis dot structure for each? I would look at SO4^2- and ClF4^-. Another way is to count the electrons around one that you know; e.g. we know CCl4 is tetrahedral. That has 4e for C and 28 e for 4Cl atoms for a total of 32e. Check the number of electrons around for the others. One should be different. That's much faster than drawing the Lewis structure for each.