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### Bond Angle

Posted: Wed May 23, 2018 2:36 pm
What determines the angle of the bonds in a molecule?

### Re: Bond Angle

Posted: Wed May 23, 2018 2:41 pm
You just said in class "These are found experimentally. You will not have to memorize"

### Re: Bond Angle

Posted: Wed May 23, 2018 7:06 pm
I think what determines the bond angles is that each atom has to be equally spaced from one another. The exact numbers are calculated experimentally, so we don't have to know them.

### Re: Bond Angle

Posted: Thu May 24, 2018 12:31 am
There are a few relative numbers set for each shape. However, the correct bond angle is determined experimentally, so we do not have to remember them.

### Re: Bond Angle

Posted: Thu May 24, 2018 5:13 pm
Molecular geometries can be specified in terms of bond lengths and bond angles. The bond length is defined to be the average distance between the nuclei of two atoms bonded together in any given molecule. A bond angle is the angle formed between three atoms across at least two bonds. The bond angles of each atom has to be equally spaced from one another. This is calculated experimentally, the closer they are the less or smaller the angle is which makes the degree smaller but you do not have to remember the exact number for all of structural planes.

### Re: Bond Angle

Posted: Fri May 25, 2018 11:43 am
When lone pairs are included on the central atom, it makes the bond angle smaller. Is this the only general trend about bond length we need to know, but no specifics?

### Re: Bond Angle

Posted: Fri May 25, 2018 12:30 pm
I believe we need to know some general angles: tetrahedral - 109.5º, linear - 180º, trigonal planar - 120º (I'm not too sure if we need to know octahedral or trigonal bipyramidal). Outside of that, we probably only need to know some trends. For example, although trigonal pyramidal has a shape similar to a tetrahedral, there is a lone pair that pushes the atoms bonded to the center closer together, creating bond angles slightly less than 109.5º (the bond angles of a tetrahedral).

### Re: Bond Angle

Posted: Sun May 27, 2018 2:56 pm
The bond angle is determined by the molecular shape of the molecule and the amount of lone pairs the molecule has. It is helpful to draw the shapes to visualize the angles better.

### Re: Bond Angle

Posted: Sun May 27, 2018 4:32 pm
You do have to know the general numbers such as 109.5 degrees for tetrahedral and 120 degrees for trigonal planar to name a few. You will also have to understand how the lone pairs will affect these angles although the exact bond angle for every molecule does not have be memorized.

### Re: Bond Angle

Posted: Sun May 27, 2018 8:18 pm
As a follow up, how do lone pairs affect bond angles? I understand that the lone pair sits more on top of the central atom - but does this always have the same affect on the angles?

### Re: Bond Angle

Posted: Sun May 27, 2018 10:19 pm
Generally lone pairs on the central atom will cause a decrease in bond angle due to the lone pair trying to repel the bonded pair of electrons.