Question

question 9 (1 point)
why do ionic formula units usually have higher melting and boiling points than covalent compounds?
the intermolecular forces in ionic formula units are weaker than those in covalent compounds
covalent molecules have higher electron affinities than ionic molecules.
ionic bonds are stronger than covalent bonds
the intermolecular forces in covalent compounds are weaker than those in ionic formula units
covalent bonds are stronger than ionic bonds

Explanation:

Ionic formula units have strong ionic bonds. Melting and boiling points depend on the strength of the forces holding the particles together. Ionic bonds are stronger than the intermolecular forces (like van der Waals forces) in covalent compounds. The first option is wrong as ionic forces (bonds) are stronger. Electron - affinity (second option) is about an atom's ability to gain an electron and not directly related to melting/boiling points here. The fifth option is incorrect as ionic bonds are generally stronger than covalent bonds (in terms of the forces relevant to melting/boiling for these compound types). The fourth option is correct as it correctly compares the intermolecular (for covalent) and bonding (for ionic, which are stronger in this context) forces.

Answer:

The intermolecular forces in covalent compounds are weaker than those in ionic formula units.