Final answer:
Option c, Sodium (Na) and Boron (B), would not typically form an ionic compound because though Boron can form ionic compounds, it is more inclined to form covalent compounds.
Step-by-step explanation:
The question asks us to identify which pair of elements would not form an ionic compound. For a pair of elements to form an ionic compound, typically one element should be a metal (which tend to lose electrons and form positive ions) and the other should be a non-metal (which tend to gain electrons and form negative ions). We examine each option:
- (a) Aluminum (Al) is a metal, and Bromine (Br) is a non-metal. They would likely form an ionic compound, AlBr3.
- (b) Magnesium (Mg) is a metal, and Sulfur (S) is a non-metal. They would likely form an ionic compound, MgS.
- (c) Sodium (Na) is a metal, and Boron (B) is a metalloid with properties of both metals and non-metals. Although Boron can form ionic compounds, it is more inclined to form covalent compounds due to its small size and relatively high electronegativity.
- (d) Potassium (K) is a metal, and Fluorine (F) is a non-metal. They would likely form an ionic compound, KF.
Based on the above reasoning, option c. Na / B is the correct answer because Sodium (Na) and Boron (B) would not typically form an ionic compound.