The shape is: trigonal bypyramidal, with 5 pairs of electrons in the outer shell. I dont understand why the bond angle changes, should'nt the angles remain the same ( 90 and 120 ) because there is an electron above and below? (sorry cant really explain)
yes, but there are 2 lone pairs above and below, so they are repelling the same amount right?, so the question is why isnt it 90?
Sorry, I didn't realise you had edited your post. The two lone pairs aren't above and below the BrF3 plane as in (a). A molecule with 3 bonding pairs and 2 lone pairs adopts a T-shape (c).
Sorry to hijack this post but could it also be drawn as having two lone pairs at the top and then the T-shape as a normal T-shape so to speak as opposed to it being on its side. I never understand this part of mark schemes - I get the structure right but never facing the right way if that makes sense?
Sorry to hijack this post but could it also be drawn as having two lone pairs at the top and then the T-shape as a normal T-shape so to speak as opposed to it being on its side. I never understand this part of mark schemes - I get the structure right but never facing the right way if that makes sense?
Yes, that's fine. It doesn't matter how you draw it - in the same way you can draw a square on it's side or standing on one of it's corners. It's still the same square
Yes, that's fine. It doesn't matter how you draw it - in the same way you can draw a square on it's side or standing on one of it's corners. It's still the same square
Ah thanks for that - I just wasn't sure as usually in the textbooks and revision books they tend to put the lone pair at the top but in mark schemes they tend to rotate the shapes around.
My question is why was this included in the Jan 2012 module when no one covered this structure. To be honest it's still wasn't clear to me, until I actually looked at it indepth, how it was made up! http://sixthsense.osfc.ac.uk/chemistry/bonding/covalent.asp
Angles aren't perfect 120 and 90 etc as in VSEPR theory lone pairs take up 'more space' than bonding pairs. This can be rationalised by considering that lone pairs are localised on the central atom whereas bonding pairs are shared between the atoms. As the lone pairs are localised they are 'nearer' the central atom and have more influence upon the shape. Axial positions (up and down) are more favorable to place large atoms than equatorial positions as the steric interactions are smaller than in the equatorial positions.