Covalent compounds are often characterized by specific properties that distinguish them from ionic compounds. Among the options provided, the statement that is untrue is c) have high melting points.
Most covalent compounds, especially those formed between nonmetals, tend to have relatively low melting and boiling points compared to ionic compounds. This is primarily due to the nature of the bonds that hold their molecules together. In covalent compounds, molecules are held together by relatively weak intermolecular forces, such as van der Waals forces or hydrogen bonding, rather than the strong ionic bonds found in ionic compounds.
Let’s look at the other options:
- a) exist as gases, liquids, or solids at room temperature: This is true, as many covalent compounds can be found in any of these states depending on the specific compound.
- b) are extremely malleable, soft, and pliable when in solid form: This is also true for many covalent compounds, particularly those like wax or certain plastics.
- d) are not good conductors of electricity: This is true as well because covalent compounds do not have free ions or electrons that can move freely, making them poor conductors of electricity.
In summary, the correct answer here is that covalent compounds do not generally have high melting points, which makes option c the untrue statement.