Final answer:
Magnesium (Mg) and chlorine (Cl) would most likely combine to form a salt, specifically magnesium chloride (MgCl2), through the transfer of electrons between a metal and a nonmetal, resulting in an ionic compound.
Step-by-step explanation:
The pair that would most likely combine to form a salt is a. Mg and Cl. This is because when these two elements combine, magnesium (Mg) can lose two electrons to form a Mg2+ ion, and chlorine (Cl) can gain one electron to form two Cl− ions, resulting in a stable ionic compound, magnesium chloride (MgCl2). This combination is based on the tendency of metals to lose electrons and nonmetals like chlorine to gain electrons, forming an ionic bond.
Option b. Ne and F would not form a salt because neon (Ne) is a noble gas and generally does not react to form compounds. Option c. Ca and C is also unlikely because calcium (Ca) typically forms ionic compounds with nonmetals rather than with carbon (C), which tends to form covalent bonds. Finally, option d. In and Fe, involving indium (In) and iron (Fe), would not form a salt as both are metals, and metals usually do not form salts with other metals.