The correct answer is option 2, which states that only the combination of Si (Z = 14) and Br (Z = 35) will form an ionic compound.

To understand why this is the correct answer, we need to have a basic understanding of ionic compounds. Ionic compounds are formed when there is a transfer of electrons between elements with different electronegativities. Electronegativity is a measure of an atom`s ability to attract electrons towards itself.

Option 1, which suggests the combination of Ca (Z = 20) and Ti (Z = 22), does not result in an ionic compound because both calcium and titanium have similar electronegativities and tend to form covalent bonds instead.

Option 3, which suggests the combination of Mg (Z = 12) and Cl (Z = 17), will indeed form an ionic compound. This is because magnesium has a lower electronegativity compared to chlorine, resulting in the transfer of electrons from magnesium to chlorine to form an ionic bond.

Therefore, option 2 is the correct answer as only the combination of Si (Z = 14) and Br (Z = 35) will form an ionic compound.

Alert - correct