Why is W(VI) more stable than Cr(VI)

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In summary, Chromium(VI) is reducing while Tungsten(VI) is not, despite their similar radii. This can be attributed to the 3d orbitals in Chromium being more strongly bound compared to the 4d and 5d orbitals in Tungsten. This trend is also observed in other groups, such as V vs. Nb or Ta, Fe vs. Ru or Os. The 5d orbitals in Tungsten are not necessarily higher, but can be seen as the result of 3d and 4d Pauli repulsion. For more information, you can research the concept of (ns) orbital energy fall due to Pauli repulsion.
  • #1
sludger13
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I'm not sure why Chromium(VI) is reducing and Tungsten(VI) isn't. I also noticed their radius is quite similar. Is that related?
 
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  • #2
I think it is due to the d-orbitals in Cr being the first ones (3d) they don't have to be orthogonal to inner shells and are therefore relatively more strongly bound than 4d or 5d orbitals in the higher periods. Similar trends can be observed in the other groups, too, e.g. V vs. Nb or Ta, Fe vs Ru or Os.
 
  • #3
So the (3d) orbitals in Tungsten are potentially higher? Is it due to (s) orbitals core repulsion?
 
  • #4
Of course not the 3d orbitals in tungsten, but the 5d orbitals.
If you want to view this as the result of a repulsion, it is rather 3d and 4d Pauli repulsion.
 
  • #5
Ok, could you place here some links... because it's better if I read something for first. The only phenomenon I'm aware of is (ns) orbital energy fall due to Pauli repulsion, and obviously this isn't the entirely same thing.
 

1. Why is W(VI) more stable than Cr(VI)?

The stability of an element is determined by its electronic configuration. In the case of W(VI) and Cr(VI), the electronic configuration of W is [Xe]4f^14 5d^4 6s^2 while that of Cr is [Ar]3d^5 4s^1. The presence of filled d-orbitals in W makes it more stable compared to Cr which has only partially filled d-orbitals.

2. How does the size of the atom affect the stability of W(VI) and Cr(VI)?

The size of the atom also plays a role in determining stability. W has a larger atomic size compared to Cr. This means that the electrons in the outermost shell of W experience less repulsion from the nucleus compared to those in Cr, making it more stable.

3. Are there any other factors that contribute to the stability of W(VI) and Cr(VI)?

Apart from electronic configuration and atomic size, the oxidation state of an element also affects its stability. W has a higher oxidation state (+6) compared to Cr (+4) in their respective compounds, making it more stable.

4. Can the stability of W(VI) and Cr(VI) be predicted using the periodic table?

Yes, the periodic table can be used to predict the stability of elements. Elements on the right side of the periodic table tend to have higher stability due to their electronic configuration and atomic size. W and Cr are both transition metals located on the right side of the periodic table.

5. How does the stability of W(VI) and Cr(VI) affect their chemical reactions?

The stability of an element can affect its reactivity in chemical reactions. In the case of W(VI) and Cr(VI), the higher stability of W makes it less reactive compared to Cr. This makes W more suitable for use in industrial processes where a stable and less reactive element is required.

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