What are the KLMN notations for #"K"# and #"Ca"#? Why is the third digit no greater than #8# for these elements???

1 Answer
Jul 25, 2017

Because there is no need for potassium or calcium to use #3d# orbitals, which would have contained up to #10# remaining electrons in the #M# "shell". For #"K"# and #"Ca"# specifically, their #3d# orbitals are currently higher in energy than the #4s#.

(That, however, changes when we get to #"Sc"#.)


Under the so-called KLMN notation,

#K := 1s#

#L := {2s, 2p}#

#M := {3s, 3p, 3d}#

#N := {4s, 4p, 4d, 4f}#

And since the #4s# orbital is singly occupied in potassium, the KLMN notation for #"K"# is

#barul(|stackrel(" ")(" ""K": overbrace(2)^(1s^2)" "overbrace(8)^(2s^2 2p^6)" "overbrace(8)^(3s^2 3p^6)" "overbrace(1)^(4s^1)" ")|)#

Likewise for #"Ca"#...

#barul(|stackrel(" ")(" ""Ca": overbrace(2)^(1s^2)" "overbrace(8)^(2s^2 2p^6)" "overbrace(8)^(3s^2 3p^6)" "overbrace(2)^(4s^2)" ")|)#