Potassium is highly reactive metal, while argon is an inert gas. How can you explain this difference based on their electron configurations?

1 Answer
May 31, 2018

Potassium needs to lose an electron to achieve noble gas configuration, while argon already has noble gas configuration.


Here are the positions of potassium and argon on the periodic table:


From this, we can see that:

  • Potassium's full electronic configuration is #1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^1#.
  • Argon's full electronic configuration is #1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)#.

Most elements tend to want to either gain or lose electrons to become isoelectronic to—or have the same electron configuration as—noble gases.

For most elements, this configuration is #ns^(2)np^6# for their valence energy level.

As such, potassium would like to lose its #1# electron in the #4s# orbital for its valence energy level to be #3s^(2)3p^(6)# (which is #ns^(2)np^(6)#) and become isoelectronic to a noble gas, argon.

As for argon, it already has a #ns^(2)np^(6)# valence shell configuration.
It's a noble gas, so it doesn't want to gain or lose more electrons.