In my notes for a module on atomic and molecular physics it has this statement: "For a given n the probability density of finding e- near the nucleus decreases as l increases, because the centrifugal barrier pushes the e- out. So the low-l orbitals are called penetrating." I just want to clear a few things up to make sure I understand this correctly. In a text book I found a good set of graphs comparing different combinations of n and l: http://img.photobucket.com/albums/v319/Adwodon/IMG.jpg Taking the n=3 set as the example, it appears to me that for l=0 the average distance is actually further from the nucleus than l=1,2. However there are 2 other peaks which seem to be roughly the same distance as the most probable distance for n=1,2 (I don't know if this is just coincidental?) So would I be totally wrong if I thought of these as sets of orbits (ie n=3 l=0 has 3 sets) and that low-l orbitals can 'penetrate' into sets of orbits which are closer to the nucleus (which are of a similar orbits to lower energy orbitals). As l increases the electron can no longer "penetrate" into lower sets due to increased angular momentum / centrifugal barrier(?), and the most probable position of the individual sets moves closer to the nucleus. For example (distances are made up and represent the location of the peaks): n=3 l=0 has Set 1 @ r=1 , Set 2 @ r=5, Set 3 @ r= 15 at n=3 l=1, set one is now inaccessible and set 2 /3 have moved closer: Set 2 @ r=4.5, Set 3 @ r= 14 and for n=3 l=2 both set 1/2 are inaccessible Set 3 @ r=12 Although I cant say I really know why the average position would move closer to the nucleus as the angular momentum is increased? Ultimately im just trying to put it into a form I can understand rather than have to learn by rote so unless my thinking is completely self defeating I don't mind if it doesn't give a totally accurate picture. Also please correct me if i'm using incorrect terminology, this is all fairly new to me and ive always been slow when it comes to buzzwords.