Water...im confused (1 Viewer)

[Loz_metalhead]

How do you work out the shapes...water would also be linear...but its bent..And I dont know how to work out if it is polar or non polar...im so sonfused. My exams are in one week.

 

[Casmira]

well you aren't precisely asked what the shape is of any random element, most likely ones you are asked to go into detail in your syllabus

for example a few ionic ones, and water, you only need to glance at them, but to be honest i dont think I was ever tested on shape of a molecule

 

[kami]

some of it is to do with Hydrogen Bonding and all that shizzle.
here's a link for you to look at since I don't think I'm the one best equipped to explain it. http://www.lsbu.ac.uk/water/

 

[Jumbo Cactuar]

Water's shape is to do with hybridisation of orbitals and electron pair repulsions. To sum it up:

Water is a bent molecule because the lone pairs of oxygen occupy orbitals in the same fashion as bonding electrons. The four occupied valence orbitals repel each other as they are occupied by like charges. To be at the lowest energy the four orbitals would be approxiamately 109.5 degrees apart through the oxygen centre. However, Valence Shell Electron Pair Repulsion Theory (VSEPR) predicts that valence shell lone pairs of electrons repel other orbitals by a greater degree, such that < HOH is less than 109.5 degrees (104.5 degrees in fact).

Water's net dipole (polarity) is a property caused by its shape and the electronegativety of the oxygen centre. The OH bonds are polar, they aren't directly opposed, so a net dipole results.

 

[Loz_metalhead]

Well the text book doesnt explain it very well. Take note that im only in year 11...so nothing advanced..I just want a quick explanation..

 

[mitochondria]

*waves at the person above Loz* I'm back! Anyway..

Hey Loz Assuming that you know the octect rule (and you should) and you know how to draw the Lewis-dot diagram for water (H₂O), you should realise that the water molecule has two lone pairs on the Oxygen atom as Jumbo Cactuar has explained.

What you also know, is that electrons repel each other and they try to get as far away from each other as possible. For this very reason, the water molecule is bent but not linear because minimal repulsion between the bonding (O-H) electrons and the non-bonding electrons cannot be achieved if the H-O-H structure is 180^o, I think the best you can do is to have the electron pairs (both bonding and non-bonding) orthogonal to each other if H₂O was linear.

It so happens that the repulsion is minimised when the electron pairs (again, both bonding and non-bonding) are arranged in a tetrahedral shape with the Oxygen atom system sitting in the middle, therefore water is bent.

Hope that helps!

 

[Dreamerish*~]

Mitochondria! Hello!!!

 

[s_t_a_r1234]

what is hybridisation. i didnt really get what you meant, but saying that water is a bent molecule due to the lone e's in the orbitals push everything away makaing it bent