To determine which atom could represent X in the molecule LiX, we need to consider the bonding behavior of lithium and the possible interactions with other elements based on their positions in the periodic table.
Lithium (Li) is an alkali metal in Group 1 and typically forms ionic bonds by losing one electron to achieve a stable electron configuration. Therefore, it tends to bond with nonmetals, which can accept electrons and typically have higher electronegativities.
Looking at your options:
- Oxygen (O): Group 16 (chalcogen), known to gain two electrons to form an oxide ion (O²⁻). Lithium can bond with oxygen to form lithium oxide (Li2O), but in a simple LiX scenario, it forms an ionic bond with oxygen, resulting in LiO⁻.
- Potassium (K): Also an alkali metal in Group 1, it would not form a compound like LiX as both elements would be metals.
- Boron (B): Group 13, typically forms covalent bonds and does not easily bond with lithium to form a stable ionic compound in the simplest form.
- Bromine (Br): Group 17 (halogen), known to gain one electron to form bromide ion (Br⁻). Lithium can readily bond with bromine to form lithium bromide (LiBr), which is a stable ionic compound.
Given these points, the best choice for X that would result in a stable molecule with lithium is:
bromine (Br).