To determine which pairs of elements are most likely to form a stable ionic bond, we need to consider the typical behavior of atoms based on their position in the periodic table. Ionic bonds typically form between metals (which tend to lose electrons and become positively charged cations) and nonmetals (which tend to gain electrons and become negatively charged anions).
Let's analyze the options:
a. Carbon (Period IVA) and Oxygen (Period VIA)
- Carbon is a nonmetal that typically forms covalent bonds rather than ionic bonds. Oxygen is a nonmetal as well. This pair is less likely to form an ionic bond.
b. Lithium (Period IA) and Fluorine (Period VIIA)
- Lithium is a metal that readily loses one electron to form a cation (Li⁺), and fluorine is a nonmetal that readily gains an electron to form an anion (F⁻). This pair is highly likely to form a stable ionic bond (LiF).
c. Magnesium (Period IIA) and Iron (Period VIIIB)
- Magnesium is a metal that typically loses two electrons to form a cation (Mg²⁺), while iron can exist in different oxidation states (Fe²⁺, Fe³⁺). However, since both are metals, they are unlikely to form a stable ionic bond together as there’s no nonmetal to accept electrons.
d. Potassium (Period IA) and Tin (Period IVA)
- Potassium is a metal that loses one electron to form K⁺, while tin is a metalloid that does not typically form anions. This pair is unlikely to form a stable ionic bond.
From the above analysis, the most likely pair to form a stable ionic bond is:
b. Lithium (Period IA) and Fluorine (Period VIIA).