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what happens when potassium forms an ion?

it gains an electron and has an octet in its outer shell.

it gains an electron and has an octet in its inner shell.

it loses an electron and has an octet in the next-lowest energy level.

it gains an electron and has an octet in the lowest energy level.

The correct answer is "It loses an electron and has an octet in the next-lowest energy level."

Explanation:

Valencia electrons are the electrons found in the last electronic layer (called valence orbitals). These electrons are what determine the ability of the atom to form bonds. When an element joins another, it does so through its valence electrons. It is also possible to say that these electrons are the electrons furthest from the nucleus of the atom, which is why they participate in chemical reactions.

An ionic bond is produced between metallic and non-metallic atoms, where electrons are completely transferred from one atom to another. During this process, one atom loses electrons and another one gains them, forming ions. Usually, the metal gives up its electrons forming a cation to the nonmetal element, which forms an anion.

In the ionic bond, when the metallic atom has a single electron in its outer layer and the non-metallic one needs an electron to complete its layer; The metallic atom yields its electron to the nonmetal for both elements. Thus the ions comply with the octet rule and, therefore, are more stable. Remember that the octet rule states that the atom is stable when it presents in its valence layer 8 electrons. This configuration is similar to that of a noble gas, which are the elements located at the right end of the periodic table.

Potassium is a metal that is in group 1 and has an electron in its last layer (layer S). Then this electron and becomes a cation. In this way it acquires the stable configuration of the argon noble gas Ar, which is the closest noble gas in the periodic table.

So, the correct answer is "It loses an electron and has an octet in the next-lowest energy level."