C not sure 100 percent but my best guess
Basically since potassium chloride is an ionic compound as it consists of a metal and a nonmetal, the potassium atom will donate one of its valence electrons to chlorine that will accept it and as a result produce oppositely charged ions, where the K + ion and the Cl - ion will attract forming an ionic bond. The compound that results is potassium chloride.
To much letters and numbers
Atomic mass is the answer!!
Explanation: An elements atomic number won’t be able to change