- Metallic bonds exhibit high electrical conductivity due to delocalized electrons.
- Covalent bonds in molecular structures do not conduct electricity because they lack free charges.
- Molecular covalent compounds typically possess weak intermolecular forces, resulting in low melting points.
- The combination of 'no conductivity' and 'low melting point' identifies the bond as covalent. The final answer is \(\boxed{\text{covalent bond and low melting point}}\).
Explanation
- Analyzing Bonding Types and Properties
The provided table contains properties of substances based on their bonding types: ionic, covalent, and metallic. We need to identify the bond type and the likely property for Row 3, given that it does not exhibit electrical conductivity.
Ionic bonds (Row 1) involve the transfer of electrons, resulting in ions that, when mobile (molten or in aqueous solution), conduct electricity and generally possess high melting points.
Next, we look at the remaining types: metallic and covalent.
Metallic bonds are characterized by delocalized electrons, which allow them to conduct electricity efficiently in the solid state. Therefore, a substance with a metallic bond is characterized by 'Yes' for electrical conductivity.
Covalent bonds involve the sharing of electron pairs between atoms, typically between non-metals. In molecular covalent compounds, the atoms are held together by strong covalent bonds within the molecule, but the molecules themselves are held together by relatively weak intermolecular forces. These compounds generally do not have free charges (ions or electrons) available to conduct electricity, leading to 'No' for electrical conductivity.
- Evaluating Row 3 Options
We have established that substances with metallic bonds typically conduct electricity, while those with covalent bonds generally do not.
Row 2 of the table indicates 'Yes' for electrical conductivity, which matches the properties of a metallic bond.
Row 3 indicates 'No' for electrical conductivity, which matches the properties of a covalent bond.
Now, we evaluate the 'Likely property' for Row 3. Compared to ionic and metallic substances, molecular covalent compounds typically have relatively weak intermolecular forces between their discrete molecules, which results in lower melting points. While there are exceptions such as network covalent solids (e.g., diamond), the most general and standard characteristic paired with covalent bonding in this context is a 'low melting point'. Thus, 'covalent bond and low melting point' is the best fit for Row 3.
- Conclusion
Comparing our findings to the given options:
- metallic bond and low melting point: Incorrect (Metallic bonds conduct electricity).
- metallic bond and high melting point: Incorrect (Metallic bonds conduct electricity).
- covalent bond and low melting point: Correct (Covalent bonds do not conduct electricity and typically have low melting points).
- covalent bond and high melting point: Less standard (Molecular covalent compounds generally have low melting points).
Therefore, the blanks in Row 3 are best filled by 'covalent bond and low melting point'. The final answer is \(\boxed{\text{covalent bond and low melting point}}\).
Examples
In everyday life, we encounter covalent compounds frequently. For example, water (\(H_2O\)) and carbon dioxide (\(CO_2\)) are molecular covalent compounds. Because they do not have free-moving charged particles, pure water is a poor conductor of electricity, and both substances have relatively low melting points—water turns from solid ice to liquid at \(0^\circ \text{C}\), and carbon dioxide sublimates directly from solid to gas at a very low temperature. Understanding these bonding properties helps scientists predict how different materials will behave in various environments.