shape of molecules (2 Viewers)

[dzzlng_07]

i dont get why some molecules are bent, some are linear, some are tetrahedrial etc... it says which ones which, but i dont know if we need to know the reasoning as to WHY its like that..

can someone help me explain the different shapes??

 

[tennille]

This is known as the VSEPR theory (Valence Shell Electron Pair Repulsion theory). Basically, valence shell electrons are meant to repel each other. Hence, in linear molecules, the atoms are placed as far away as possible. The reason for the difference in geometry of different molecules is due to the fact that they consist of different numbers of atoms on the central atom. With tetrahedral molecules, there are four atoms bound to the central atom. As a result, there is less "flexibility" to place the atoms as far away as possible (~109 degrees), in contrast to linear molecules when they are 180 degrees apart.

Also, lone pairs repel more than bond pairs. This is the reason why some molecules are bent and why others are linear.

 

[Forbidden.]

Those who want to determine the distance of electrons from each other ..

In Physics:

North pole repels North Pole
South Pole repels South Pole

North Pole attracts South Pole
North Pole attracts South Pole

In Chemistry:

"Electrons like to stay far away from each other", says my Chemistry teacher.

Let's say:

If there was 3 electrons in an outershell there would be 120⁰ from each other.

Here is my way of precisely determining electron distance

Distance of electrons = Revolution / no. of electrons

You know a revolution is 360⁰ right ?

If there were 5 electrons in a shell, divide 360 by 5 and you get 72⁰ (360/5=72⁰), so the 5 electrons will stay 72⁰ away from each other..

Except if the dipole/monopole forces apply ...

Check out hsc.csu.edu.au if you have not been there ...

Is this the correct form to write this hydrocarbon compund if there was 2 chlorine atoms, 4 methyl compounds on propane ?
(Adding numbers as an example)

1-dichloro-2-dimethyl-propane

 

[rama_v]

Is this the correct form to write this hydrocarbon compund if there was 2 chlorine atoms, 4 methyl compounds on propane ?
(Adding numbers as an example)

1-dichloro-2-dimethyl-propane

You need to indicate the numbers as many times as they appear. So for your example it would be
1,1-dichloro-2,2-dimethylpropane : no dashes in between words, only between words and numbers.

 

[Gavvvvvin]

Here is my way of precisely determining electron distance

Distance of electrons = Revolution / no. of electrons

You know a revolution is 360⁰ right ?

If there were 5 electrons in a shell, divide 360 by 5 and you get 72⁰ (360/5=72⁰), so the 5 electrons will stay 72⁰ away from each other..

Err no, that would only work if the electron pairs magically stayed in one plane.

 

[Forbidden.]

You need to indicate the numbers as many times as they appear. So for your example it would be
1,1-dichloro-2,2-dimethylpropane : no dashes in between words, only between words and numbers.

Thanks, that was good help, I have been waiting for three Chemistry lessons to know how to write the names down in a proper form.

 

[Xeno]

Err no, that would only work if the electron pairs magically stayed in one plane.

Yes I agree that the angles between the bonds would not = 72 degrees.

If there were 5 regions of electron density around the central atom (ie we could have 5 bonds, or 5 lone pairs, or any combination of these) then possible shapes could be:
3 regions distributed in a plane around the central atom (the bond angles between each region being 120 degrees). The final 2 regions are distributed above and below this plane: the angle between each region of density and the plane is 90 degrees.
An example of a molecule with this geometry is Phosphorous pentachloride.