Summary
Highlights
Ionic bonding occurs between metal and non-metal atoms, like sodium and chlorine. Metal atoms typically have 1-3 outer electrons, while non-metal atoms have 4-8. Atoms desire a full outer shell, so the metal atom donates its electron to the non-metal atom. This transfer creates oppositely charged ions (positive metal ion, negative non-metal ion) that attract each other, forming a strong ionic bond. These bonds lead to high melting points in ionic compounds, which often form giant lattice structures.
Covalent bonding occurs between non-metal atoms, as seen in water (H₂O). Instead of transferring electrons, atoms share electrons to achieve a full outer shell. For example, oxygen shares electrons with two hydrogen atoms. The attraction between the negatively charged shared electron pairs and the positive nuclei forms the covalent bond. While covalent bonds are strong, simple covalent compounds have weak intermolecular forces, resulting in low boiling points. However, giant covalent compounds like diamond have very high melting points due to strong covalent bonds throughout their structure.
Metallic bonding occurs between metal atoms, such as iron. Metal atoms share their outer shell electrons collectively, forming a 'sea of delocalized electrons' that can move freely throughout the structure. The positive metal nuclei are held together by this sea of mobile electrons, acting like a strong glue. This strong metallic bonding explains why metals generally have very high melting points.