Question

Which is more stable vanadium or chromium? And why?

Answer 1

It is not a physically reasonable comparison to make. They are different elements, and each of them are as stable as that element can be in their respective ground states.

Chemical stability is a thermodynamic phenomenon, and is not indicative of chemical reactivity, which is kinetic in nature.

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Now, if you meant which element is more prone to participating in chemical reactions, it would usually be vanadium, as it has lower ionization energies for comparable oxidation states (up to `+V`).

If we were to compare their ionization energies, we could see that the atom with the lower ionization energy has a greater tendency to lose the `n`th electron in the `+(n-1)` charge state to form the `+n` charge state.

Using data from NIST, I get:

However, `"Cr"` can attain the higher oxidation state, at which point it becomes more reactive as `"Cr"^(+5)` and `"Cr"^(+6)`, forming the `+VI` and `+VII` oxidation states, respectively.