Which statement best describes the properties of covalent compounds?
1. they are always solid at room temperature, are brittle, and have a high melting point.
2. they may be gases, liquids, or solids at room temperature, and have a low melting and boiling point.
3. they are always composed of an equal proportion of cations to anions.
4. they are always liquid at room temperature, and have a high melting and boiling point.
5. they are good conductors of heat and electricity, and are ductile and malleable.