(b) A substance, XY, formed from two different elements, melts at −33 °C. Is XY likely to be a covalent or an ionic substance?

Key Concepts

Covalent vs. Ionic Bonds

Covalent bonds form when two nonmetals share electrons, resulting in molecules with lower melting and boiling points. In contrast, ionic bonds occur between metals and nonmetals, where electrons are transferred, creating charged ions that attract each other, typically resulting in higher melting points.

Melting Point as an Indicator

The melting point of a substance can provide insight into its bonding type. Generally, substances with ionic bonds have higher melting points due to the strong electrostatic forces between ions, while covalent compounds often have lower melting points due to weaker intermolecular forces.

Properties of Molecular Compounds

Molecular compounds, which are often formed by covalent bonds, tend to have distinct properties such as lower melting points, volatility, and poor electrical conductivity in solid form. The melting point of −33 °C suggests that XY is likely a molecular compound, indicating it is more likely to be covalent.