In order to write the Potassium electron configuration we first need to know the number of electrons for the K atom (there are 19 electrons). When we write the configuration we'll put all 19 electrons in orbitals around the nucleus of the Potassium atom.
In writing the electron configuration for Potassium the first two
electrons will go in the 1s orbital. Since 1s can only hold two
electrons the next 2 electrons for Potassium go in the 4s orbital. The
next six electrons will go in the 2p orbital. The p orbital can hold up
to six electrons. We'll put six in the 2p orbital and then put the next
two electrons in the 3s. Since the 3s if now full we'll move to the 3p
where we'll place the next six electrons. We now shift to the 4s
orbital where we place the remaining electron. Therefore the Potassium
electron configuration will be 1s22s22p63s23p64s1