Final answer:
In KCl, the valence electron from potassium is transferred to chlorine to form an ionic bond, where potassium becomes a K+ cation and chlorine gains an electron to become a Cl- anion.
Step-by-step explanation:
The distribution of valence electrons in KCl, which is potassium chloride, involves transferring the valence electron of potassium (K) to chlorine (Cl) to form an ionic bond. Potassium, with an atomic number of 19, has one electron in its valence shell, which it loses to achieve a stable electron configuration, becoming a potassium ion (K+). This is because potassium is more likely to donate an electron than to acquire more, due to its placement in the periodic table. Conversely, chlorine, with an atomic number of 17, has seven valence electrons and needs one additional electron to fill its valence shell and become a chloride ion (Cl-), achieving the octet rule.
By donating its electron, potassium becomes a cation, while chlorine accepts this electron to complete its octet, thus forming an anion. These ions are attracted to each other due to their opposite charges, forming a strong ionic bond. In KCl, therefore, the valence electron from potassium becomes a lone pair on chlorine, which now has a filled valence shell as a result.