Basic atom & molecule physics

  • Thread starter Glenn
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  • #1
Glenn
1. Why exactly does a covalent bond work? I understand how the electrons fill up the shells and so forth, but why does it work. Is the bond caused by the two atoms "competing" for the same electron that pulls them together? Is that a correct analogy?

2. Are electrons EXACTLY the same charge as the proton?


3. How is the bond angle in H2O predicted by physics?

4. What dictates how many electrons can occupy a shell?

Thanks,
Glenn
 
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  • #2
1. You can kind of think of it like that, yeah. Atoms like to fill their orbitals and if, for example, two hydrogen atoms can share each other's electron then they'll both have complete 1s orbitals. There's really not a great simple way of explaining it without resorting to quantum mechanics. And remember it's not one electron they share, but a pair. There's two electrons in a bond.

2. yes. If not you'd see a net charge in bulk material.

3. With two hydrogen atoms and two lone pairs, according to VSEPR you'd predict that the bond angle would be 109.5 degrees, a perfect tetrahedron. The actual bond angle is something like 105.7 degrees. The hand waving explanation being that the two lone pairs repel each other a little more than the hydrogens atoms, squeezing the latter together.

4. quantum mechanics.
 
  • #3
Simfish
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4. What dictates how many electrons can occupy a shell?
Doesn't it has to deal with Pauli's Exclusion Principle of Quantum Mechanics?
 
  • #4
GCT
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1. Why exactly does a covalent bond work? I understand how the electrons fill up the shells and so forth, but why does it work. Is the bond caused by the two atoms "competing" for the same electron that pulls them together? Is that a correct analogy?

Yeah, something like that. Think of Columb's law. Nevertheless notice that we cannot predict the exact position of the electrons. Nevertheless, this makes sense since a electron which occupied one position with respect to its atoms would be less stable; think of it as the electron working to make sure that the atoms stay together (although the electron does not have a motive of its own).

2. Are electrons EXACTLY the same charge as the proton?
I believe so.

3. How is the bond angle in H2O predicted by physics?
Same as in chemistry. Quantum mechanics.

4. What dictates how many electrons can occupy a shell?
Quantum mechanics, most likely beyond your scope at this point.

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