Potassium K and chlorine Cl are elements found in the periodic table. Potassium is an alkali metal in Group 1, while chlorine is a halogen in Group 17. To predict the reactivity of these elements when combined to form potassium chloride KCl , we need to consider their electronic configurations.Potassium K has an atomic number of 19, and its electronic configuration is 1s 2s 2p 3s 3p 4s. It has one electron in its outermost shell 4s .Chlorine Cl has an atomic number of 17, and its electronic configuration is 1s 2s 2p 3s 3p. It has seven electrons in its outermost shell 3p and needs one more electron to achieve a stable noble gas configuration.When potassium and chlorine react, potassium loses its one valence electron in the 4s orbital, forming a positively charged ion K . Chlorine gains this electron, filling its 3p orbital and forming a negatively charged ion Cl . This transfer of electrons results in an ionic bond between the potassium and chlorine ions, creating potassium chloride KCl .The reactivity of potassium and chlorine when combined to form KCl is predicted to be high due to the strong electrostatic attraction between the ions. This is because potassium readily loses its valence electron, and chlorine has a high affinity for gaining an electron. The resulting ionic compound, KCl, is stable and has a high lattice energy, which is a measure of the strength of the ionic bond.