Question

______ compounds tend to be harder and more brittle and to have higher boiling points than materials containing only covalently bonded atoms.

Answer 1

Ionic compounds are typically harder, more brittle, and have higher boiling points than covalent compounds due to the strong ionic bonds in a 3D lattice structure. Most covalent substances are softer with lower melting and boiling points, though exceptions like diamond do exist.

Step-by-step explanation:

Ionic compounds tend to be harder and more brittle and to have higher boiling points than materials containing only covalently bonded atoms. This is due to the strong ionic bonds formed between ions, which constitute a 3D crystal lattice structure, making these compounds typically hard and with high melting points. For instance, NaCl has a melting point of approximately 801 ℃ and a boiling point of approximately 1465 ℃, showcasing the robust nature of ionic interactions.

Conversely, covalent compounds have molecules held together by weaker intermolecular forces, resulting in lower boiling and melting points, with the compounds being generally softer and less brittle. They do not conduct electricity in their solid or liquid states because they lack free-moving electrons, which is unlike the ionic compounds that can conduct electricity when melted or dissolved in water.

Certain covalent compounds such as diamond, which is composed of carbon atoms in a 3D network of covalent bonds, present an exception, being extremely hard and having a very high melting point of approximately 4027 ℃. However, most molecular covalent substances cannot compare with the typical hardness or the high melting and boiling points of ionic compounds.