Why isn't ClF3 trigonal planar?

[prakhargupta3301]

I know ClF3 has triagonal bi-pyramidal arrangement and T-shape molecular geometry. (as shown in first diag.). However, it can also be 2nd case. In this one, the shape will be triagonal planar. Also, electrons will be farthest. So why isn't ClF3 like second case?

 

[DrDu]

In VSEPR theory, non-bonding electron pairs are sterically more demanding than bound electron pairs. In the first formula, each non-bonding electron pair has only two neighbours in a 90 degree separation while in the 2nd one, each has 3. Whether the distance between the two non-bonding pairs is 120 or 180 degrees will be rather irrelevant compared to the next neighbour repulsion.

 

[prakhargupta3301]

I get what you mean. Thank you.
But would you be kind enough to explain what

'sterically more demanding than bound electron pairs'

means?
[I did look up the meaning of steric but the meaning still isn't clear]
Thanks.

 

[Borek]

Need more space for themselves, occupy larger volume.