Unpaired Electrons in Potassium

Unpaired electrons are those electrons in an atom which occur alone in the orbitals.

Let me explain this, atoms have orbits which are called KLMN and then these orbits have subshells which are called 1s, 2s, 2p etc. Further these subshells have orbitals each of which can contain either 1 or 2 electrons. So if an orbital have one electron instead of 2, that single electron will be counted as unpaired electron.

2 in 2s

3 in 2p
2 in 3s

3 in 3p

5 in 3d
2 in 4s

3 in 4p

5 in 4d

7 in 4f

Best way to determine how many unpaired electrons are there in an atom is to just write it’s electron configuration and then draw its orbital diagram.

From orbital diagram we can easily calculate how many unpaired electrons are there.

So let’s first write electron configuration of potassium and then draw it’s orbital diagram.

Writing electron configuration of Potassium

Potassium atom in total have 19 electrons, to write down the electron configuration of potassium, the first two electrons would go into the 1s orbital. Because the 1s orbital can only accommodate two electrons, next two electrons are placed in the 2s orbital, next 6 electrons are placed in 2p orbital. Out of 9 remaining electrons, 2 would go into 3s orbital, 6 electrons are placed in 3p orbitals and remaining one is placed in 4s orbital. Putting all this together, electron configuration of potassium is 1s2 2s2 2p6 3s2 3p6 4s1. Which can also be written as [Ar] 4s1 where [Ar] represents electron configuration of noble gas Argon.

If your interested in knowing what’s full process of figuring out electron configuration of Potassium, you can check this article – Writing Electron Configuration of Potassium.

Video describing how to write Electron Configuration of Potassium

Drawing Orbital Diagram of Potassium

So electron configuration of potassium is 1s2 2s2 2p6 3s2 3p6 4s1 let’s draw orbital diagram now. But before doing this we need to keep in mind that as per Aufbau’s Principle increasing order of energy of different subshells is 1s < 2s < 2p < 3s < 3p.

Therefore in orbital diagram 1s should be written at bottom showing minimum energy while 3p should be written at top showing maximum energy.

Moreover for filling up these orbitals we need to follow a rule called Hund’s Rule of Multiplicity which state that pairing of electrons in orbitals start once each orbital in that subshell have one electron.

Video describing how to draw Orbital Diagram of Potassium
Diagram showing Distribution of electrons in orbitals of Potassium atom showing 1 unpaired electron

From above orbital diagram its clear that out of total 19 electrons in Potassium atom, 18 are paired in different orbitals but there is just one electron in 4s orbital which is alone. Therefore potassium have 1 unpaired electron.

SubshellNumber of OrbitalsNumber of electronsPaired or Unpaired
2p36Each of three orbitals
have paired electrons
3p36Each of three orbitals
have paired electrons

Properties of Potassium due to Unpaired Electron

From electron configuration of potassium 1s2 2s2 2p6 3s2 3p6 4s1 and its orbital diagram it is clear that potassium have one unpaired electron which is located in 4s orbital.

But as this electron is alone in 4s orbital, therefore potassium atom can loose this electron and then its electron configuration will change from 1s2 2s2 2p6 3s2 3p6 4s1 to 1s2 2s2 2p6 3s2 3p6 which is electron configuration of noble gas Argon and it is more stable as compared to electron configuration of potassium.

Therefore due to presence of one unpaired electron, potassium can become monovalent cation (K+).

Also due to the fact that there’s one unpaired electron in potassium, it is paramagnetic in nature which means it is attracted by poles of magnet.


Number of unpaired electrons in Potassium?

Based upon electron configuration 1s2 2s2 2p6 3s2 3p6 4s1 and orbital diagram of potassium, number of unpaired electrons in it is one and this unpaired electron is located in 4s orbital.

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