Why you only put 8 electrons in the outer cell of pottassium?

Potassium (K) has an atomic number of 19, meaning it has 19 electrons. The electron configuration of potassium is 2, 8, 8, 1, indicating that it has 8 electrons in its second energy level (the outer shell) and 1 electron in its third energy level. According to the octet rule, elements tend to be more stable with 8 electrons in their outer shell, which is why potassium's configuration shows 8 in the outer shell, even though its valence shell can hold more. The single electron in the third shell is readily lost, making potassium a highly reactive alkali metal.