Covalent Bonding

Summary and Exam Tips for Covalent Bonding

Covalent Bonding is a subtopic of Principles of Chemistry, which falls under the subject Chemistry in the Edexcel IGCSE curriculum. A covalent bond is defined as the electrostatic attraction between a bonding pair of electrons and the two nuclei of the bonded atoms. Non-metallic elements form simple molecules with covalent bonds, such as $\text{H}_2$, $\text{Cl}_2$, $\text{H}_2\text{O}$, $\text{CH}_4$, $\text{NH}_3$, and $\text{HCl}$, through the sharing of electron pairs to achieve a stable configuration. More complex covalent molecules include $\text{N}_2$, $\text{C}_2\text{H}_4$, $\text{CH}_3\text{OH}$, and $\text{CO}_2$.

In macromolecules like diamond, each carbon atom is covalently bonded to four others, resulting in a very hard structure with a high melting point, making it suitable for cutting tools. Graphite, on the other hand, consists of carbon atoms bonded to three others, forming layers that can slide over each other, making it useful as a lubricant and conductor. Silicon dioxide features silicon atoms bonded to four oxygen atoms, and is commonly added to foods and supplements.

Exam Tips

• Dot and Cross Diagrams: Focus on showing only the electron's outer shell.
• Intermolecular vs. Covalent Bonds: Remember that while molecules are attracted to each other by intermolecular forces, the atoms within them are held together by covalent bonds.
• Properties of Macromolecules: Understand the structure and properties of diamond, graphite, and silicon dioxide, and their practical uses.
• Complex Molecules: Be familiar with the electronic arrangements in molecules like $\text{N}_2$ and $\text{CO}_2$.
• Element Symbols and Ratios: Practice using element symbols and understanding the relative number of atoms in compounds like $\text{NaCl}$.