which of the molecule does not exibit TETRAHEDRAL arrangement of electron pairs?

which of the molecule does not exibit TETRAHEDRAL arrangement of electron pairs? (a)H20 (b)SiCl2 (c)NH3 (d)None of these

draw the lewis structure of each of the given molecules..

In case of H2O there are 4 pairs of electron around the central atom oxygen but two of them are paired and two are lone paired and in order to exhibit the tetrahedral geometry there must be 4 bonding pair around the central atom.

In case of SCl2 the central atom sulfur has four electron pair aorund the it but again 2 are bonded pair and two non bonding so it will not exihibit the perfect tertrahedra geometry, 

In case of NH3 there are again 4 pair of electrons around the central nitrogen atom but three of them are paired and one lone paried.

 

I believe it is talking about the arrangment of electrons rather than atoms so you could say H2O is tetrahedral arrangment of electrons. Roughly. 2 are bonding to H atoms and 2 are lone pairs but the geometry you could say is tetrahedral. Is that right?
 
And then the case of SiCl2 is the first response missed that it is Si and not S atom. For Si atom there would only be 4 valence electrons like with carbon but maybe the d electrons could be involved also? I'm not sure. Maybe if I knew the bond angles I could hindsight rationalize but I am not sure I could predict.
 
I will report back later this week :)