Answer:
Potassium is too reactive to exist as a pure element in Earth's environment.
Step-by-step explanation:
Potassium has a single electron in it's outermost energy shell, in an s orbital: [Ar}4s^1
If potassium loses that electron, it would have a complete outer shell of electrons, just like Argon. This is a much lower energy state - all of the elements in the first column of the periodic table exhibit a tendency to readily given up their lone electron in the outermost energy shell. When this happens, it become an ion with a positive charge: K^+1. This is also unstable and the potassium ion will attract other elements or compounds to form structures such as salts (e.g., KCl or K2SO4). As long as there is something nearby, the potassium will first give up an electron to an electron-loving element such as chlorine (Cl) and then combine with a negatively-charged ion or group nearby. See the attached table for relative element reactivities for several metals. The top three are all in Group 1 (Alkali metals).