Valence electrons

[Gwynneth Orlino 1B]

I know that the number of valence electrons for s- and p-block elements can be determined by it's group number. Why doesn't this apply to the d-block and how do you find the number of valence electrons for those elements?

[205458163]

A valence electron is an outer shell electron that is associated with an atom, so we only count the outer most shell's electrons as valence electrons.

[Radha Patel 4I]

Elements in the d block are transition metals, so they normally express valence electron from the s orbital. For example, Fe has 2 valence electrons because the electron configuration is 1s^2 2s^2 2p6 3s2 3p^6 4s^2 3d^5. Notice that both ns^2 have 2 electrons so we have 2 valence electrons. Another example is Chromium, which is [Ar] 4s^1 3d^5 so it has 1 valence electron.

[Gwynneth Orlino 1B]

I saw that Chromium actually has 6 valence e- so the electrons in the s- and d- orbitals for the outer shell were counted. Why is that?

[Karina Vasquez 1D]

Elements in the d block are transition metals, so they normally express valence electron from the s orbital. For example, Fe has 2 valence electrons because the electron configuration is 1s^2 2s^2 2p6 3s2 3p^6 4s^2 3d^5. Notice that both ns^2 have 2 electrons so we have 2 valence electrons. Another example is Chromium, which is [Ar] 4s^1 3d^5 so it has 1 valence electron.

So would only those elements have two/one valence electrons, because the s-orbital can only hold up to two?