[bubaKazouba]

I wanted to ask about the electronic configuration of scandium (atomic number 21)
it's written in wikipedia its [1s2 2s2 2p6   3s2 3p6 3d1   4s2]
why can't it be [1s2   2s2 2p6   3s2 3p3 3d5   4s1],like that it will be more stable as the 3d is half full so its stable and 3p/4s are also half full
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another question,I studied that most transition metals have more than one valency,does that mean they have more than electronic configuration in the atom state or, more than one electronic configuration in the ionic state?

Thanks in advance

[Hunter2]

Orbitals are filled in order s,p,d,f. Your suggestion gives the wrong order.

[ramboacid]

I've never seen a p orbital give it's electrons to a d-orbital like you suggest. Usually this only happens for (n)d and (n+1)s orbitals.

For your second question, they have multiple valency as ions. Atoms by definition can't be charged, and having multiple valency for an atom means it would have a different number of protons and electrons in one of those valencies. An example is how copper can form Cu¹⁺ and Cu²⁺ ions, but copper atoms will always have the same number of electrons as they do protons and thus have no charge.