Which of the following is likely to be least stable?

• (A) Ca₄₀
• (B) Mn₅₅
• (C) Sn₁₁₉
• (D) Al₃₀

To determine which of the given compounds is likely to be the least stable, we need to consider their atomic structures and bonding characteristics.

Analyzing the Options

• Ca₄₀: Calcium typically forms stable compounds, but in such a high quantity, it may lead to instability due to excessive electron repulsion.
• Mn₅₅: Manganese can exhibit various oxidation states, but a large cluster like this could be unstable due to its complex electron configuration.
• Sn₁₁₉: Tin is generally stable, but a large number of atoms might lead to instability in certain configurations.
• Al₃₀: Aluminum tends to form stable structures, but a large aggregation could also introduce instability.

Conclusion on Stability

Among these, Mn₅₅ is likely to be the least stable due to the complexity of manganese's oxidation states and the potential for instability in such a large cluster. Therefore, option (B) is the best choice for the least stable compound.