How many electrons are unpaired in
K

Explanation

There is 1 unpaired electron. The potassium contains 19 electrons.
The electronic configuration is `1s^(2), 2s6(2), 2p^(6), 3s^(2), 3p^(6) , 4s^(1)` or
The 1s, 2s, 2p, 3s and 3p subsheels are completely filled with two electrons with both spins. The `19^(th)` electron enters into 4s subshell instead 3d subshell. This is due to lower energy of 4s subshell than 3d subshell.