How do you draw electron orbital diagrams?

1 Answer
Jul 25, 2016

You use lines for orbitals and arrows for electrons.


Something simple is #"He"#, whose configuration is #1s^2#. So, you fill one orbital with two electrons, as is the maximum for one #s# orbital.

#1s^2#:

#color(white)([(color(black)(ul(uarr darr))),(color(black)(1s))])#

If you add more orbitals, you include their relative energies. Say you have #"Li"#. Then you have a #2s# orbital at a (significantly) higher energy.

#1s^2 2s^1#:

#color(white)([(color(black)(ul(uarr color(white)(darr)))),(color(black)(2s))])#

#" "#
#" "#

#color(white)([(color(black)(ul(uarr darr))),(color(black)(1s))])#

With #"B"#, you introduce the #2p# orbital, which is even higher in energy than the #2s#. There are also three of them, instead of just one.

#1s^2 2s^2 2p^1#:

#color(white)([(color(black)(ul(uarr color(white)(darr)))),(color(black)(2p_x))]) color(white)([(color(black)(ul(color(white)(darr) color(white)(darr)))),(color(black)(2p_y))]) color(white)([(color(black)(ul(color(white)(darr) color(white)(darr)))),(color(black)(2p_z))]) #

#color(white)([(color(black)(ul(uarr darr))),(color(black)(2s))])#

#" "#
#" "#

#color(white)([(color(black)(ul(uarr darr))),(color(black)(1s))])#

Filling up the #2p# orbitals some more, let's look at #"F"#. You add one electron at a time to each #p# orbital to maximize total spin, as per Hund's Rule, and then pair them up afterwards.

#1s^2 2s^2 2p^5#:

#color(white)([(color(black)(ul(uarr darr))),(color(black)(2p_x))]) color(white)([(color(black)(ul(uarr darr))),(color(black)(2p_y))]) color(white)([(color(black)(ul(uarr color(white)(darr)))),(color(black)(2p_z))]) #

#color(white)([(color(black)(ul(uarr darr))),(color(black)(2s))])#

#" "#
#" "#

#color(white)([(color(black)(ul(uarr darr))),(color(black)(1s))])#

And that should cover the general idea.