Why does K⁺ have 0 valence electrons?

If an electron is removed from an atom of $\ce{K}$, why does it then have 0 valence electrons as it states in my General Chemistry textbook? I would think that if this happened, it would have the same exact electron configuration as $\ce{Ar}$, which has 8 valence electrons, correct? What's going on here?




What you say is correct. The [Ar] configuration we are left with does have 8 valence electrons. But I think it is just semantics. Elemental potassium has an [Ar] 4s1 electron configuration. One would say it has one valence electron. If we take that one valence electron away, it makes sense to say that it now has zero valence electrons because "1 - 1 = 0". 


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You are correct in that it has 8 valence electrons, not 0. If we look at the electron configuration of potassium (K), we see that it has one electron: [Ar]4s1. Obviously, removing that electron gives us [Ar] (same configuration as K1+), which is a noble gas and has 8 electrons. 


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Valence electrons are generally regarded as being 'the outermost electrons' for a given atom. Therefore, with neutral potassium, there is one valence electron. If we take away the outermost electron, we now have a new set of outermost electrons being the 8 electrons in the 3s and 3p orbitals. Ron is correct in his assessment of semantics.


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I think you need to consider that if you take last electron from the orbital it's there, but it's empty. Orbital itself is a bit abstract thing and if you accept that it can be empty then you can have 0 valence electrons - that's why your book says what it says.


If I'm not right it will be a lesson for me too :)


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