[reyrey389]

Here is the electron config. for Iron (Fe) 1s2 2s2 2p6 3s2 3p6 4s2 3d6.  I have two questions about this I've been on for hours....

#1 Which subshell (4s or 3d) has the highest subshell?
-You can say that the 3d has higher energy because you write it out later than the 4s (4s is filled before 3d)
-Then again, you can say that the 4s has higher energy because (4, the coefficient, tells us we are in the 4th energy level). 4 is the highest coefficient in that configuration, so the fourth energy level is the outermost.

So which should I follow - the first or the second?

#2 I have been also having trouble finding valence electrons for transition elements
In that configuration I displayed do we say that the valence electrons for Fe is 2? If so, will it always be in the sub shell of the highest coefficient (energy lvl). If I'm not mistaken this means to find the valence of a transition element you will look at the "s" subshell? BUT, since it is in the d-block it has filled the s, so the s will always be 2 for transition elements, so they all have 2 valence electrons?


Any help would be appreciated

[vmelkon]

From
http://en.wikipedia.org/wiki/Valence_electrons

However this simple method does not work for transition metals, which have incomplete nd (i.e. 3d, 4d or 5d) subshells whose energy is normally comparable with that of the (n+1)s electrons.

Towards the right of each transition metal series, the d electrons descend to lower energies and have less valence electron character.

For zinc and succeeding elements, the 3d subshell is complete and the 3d electrons are considered core electrons.