How are angles in molecules calculated?

In summary, the bond angle in methane and similar molecules with an atom bonded to four other atoms (such as carbon with four hydrogen atoms) is 109.5°. This is due to the VSEPR theory, which states that the bonds will spread out as far as possible. To understand why this angle is 109.5°, one can refer to resources such as the provided link.
  • #1
IDK10
67
3
I understand how angles are calculated in compounds where an atom is bonded to 2, 3, 5, and 6 bonds (bond pair + lone pair). But how do they work out the angle of a compound where an atom has 4 bonds (i.e. methane), in this case the carbon atom, has a H-C-H angle of 109.5°
 
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  • #2
Please elaborate, I fail to see how it is different.
 
  • #3
Borek said:
Please elaborate, I fail to see how it is different.
In methane and any other compound containing an atoms which only has 4 bond pairs and 0 lone pairs of electrons. The bond between the three atoms (in the case of methane, it is the H-C-H bond angle), it is 109.5°, I was wondering how they worked that out.
 
  • #4
And how they worked out the value for water molecule, or for any other molecule with any number of bonds and/or lone pairs?

I don't see why you say you know how to deal with other molecules, but you think this particular molecule is different.
 
  • #5
Borek said:
And how they worked out the value for water molecule, or for any other molecule with any number of bonds and/or lone pairs?

I don't see why you say you know how to deal with other molecules, but you think this particular molecule is different.
I'm not saying that, I'm asking how they first got the bond angles for an atom with 4 bond pairs, I'm just giving methane as an example.
 
  • #6
Sorry, I still fail to see where the problem is.

You know how to calculate angle for atom bonded to two other atoms. Can you explain how it is done?

You know how to calculate angle for atom bonded to three other atoms. Can you explain how it is done?
 
  • #8
Comeback City said:
The C-H bonds want to be as far apart from each other as possible, as is stated by VSEPR, so they spread out to that 109.5 °. If you are asking why it is 109.5, then

We don't know what he is asking. That's what I am trying to find out.
 
  • #9
Borek said:
We don't know what he is asking. That's what I am trying to find out.
Good call :cool:
 
  • #10

1. What is the purpose of calculating angles in molecules?

The purpose of calculating angles in molecules is to determine the geometric arrangement of atoms within a molecule. This information is important for understanding the properties and behavior of molecules, as well as predicting their reactivity and interactions with other molecules.

2. What factors influence the angles in a molecule?

The angles in a molecule are influenced by a variety of factors, including the types of atoms present, their relative positions, and the bonding patterns between them. Additionally, the presence of lone pairs of electrons and the overall molecular shape can also affect the angles.

3. How are angles in molecules calculated?

Angles in molecules are typically calculated using computational methods, such as molecular orbital theory or quantum mechanics. These methods involve solving complex mathematical equations to determine the energy and stability of different molecular structures, which in turn provide information about the molecular angles.

4. Can angles in molecules be measured experimentally?

Yes, angles in molecules can be measured experimentally using techniques such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. However, these methods may not always provide precise measurements and may be limited to certain types of molecules.

5. How do different angles affect the properties of a molecule?

The angles in a molecule can greatly influence its properties, such as its polarity, bond strength, and reactivity. For example, smaller angles in a molecule may result in stronger bonds and a more compact shape, while larger angles can lead to weaker bonds and a more open structure. Additionally, the angles can also affect the overall polarity of the molecule, which can impact its solubility and interactions with other molecules.

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