Covalent Bonding & Structures | A-level Chemistry | OCR, AQA, Edexcel

Covalent Bonding & Structures in a Snap! Unlock the full A-level Chemistry course at http://bit.ly/33IqQmg created by Ella Buluwela, Chemistry expert at SnapRevise. SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks. Sign up today and together, let’s make A-level Chemistry a walk in the park! The key points covered in this video include: 1. What is a Covalent Bond? 2. Dot-Cross Diagrams 3. Types of Covalent Bond a) Single b) Multiple c) Dative 4. Covalent Structures What is a Covalent bond? Strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. Usually occurs between 2 non-metals. Dot-Cross Diagrams: Covalent Bonds Pair of electrons is shared between the two chlorine atoms. Both chlorine atoms have obtained a full outer shell. Single Covalent Bonding Covalent bond involves one shared pair of electrons. Multiple Covalent Bonding Covalent bond involves more than one shared pair of electrons. 2 shared pairs of electrons. Double Bond. 3 shared pairs of electrons. Triple Bond. Dative Covalent Bonding One atom donates both of the electrons in the covalent bond. Dative covalent bonds are equivalent to other covalent bonds. They are also known as coordinate bonds. Structures of Covalent Compounds Simple Molecular Lattice. Giant Covalent Lattice. Simple Molecular Substances Made up of small molecules. Simple molecules, In solid state, exist as a lattice. Within each molecule, the atoms are tightly held together by covalent bonds. Between the molecules, weak intermolecular forces of attraction act. Example: Water. Ice, the solid state, is a lattice, Within the H2O molecule, the atoms are held together by strong covalent bonds, Between the molecules of H2O in the lattice, weak intermolecular forces of attraction exist. Properties of Simple Molecular Substances Low Melting and Boiling Points. Simple molecular structures have a low melting and boiling points. Weak intermolecular forces of attraction act between molecules. Small amount of energy needed to disrupt these forces, This results in a low melting and boiling point. Solubility. Simple molecular substances are soluble in non-polar solvents. ‘Like dissolves like’. The weak intermolecular forces of attraction between the molecular of the non-polar solvent are similar to that in simple molecular substances. These forces are able to act between the molecules of the simple molecular substance and the solvent. Electrical Conductivity. Simple molecular substances are non-conductors. No charged particles that are free to move and carry charge. Giant Covalent Substances Atoms are joined to adjacent atoms by strong covalent bonds. Network of covalent bonds. Giant Lattice is formed. Lots of strong covalent bonds throughout the structure. Example: Diamond, Graphite, Silica (Silicon Dioxide) Properties of Giant Covalent Substances High Melting and Boiling Points. Strong covalent bonds exist throughout the lattice. Lots of energy is required to break these bonds between atoms. This results in a high melting and boiling point for giant covalent substances. Solubility. Giant covalent substances are insoluble in non-polar and polar solvents. Strong covalent bonds are not disrupted by either type of solvent. Electrical Conductivity. Giant covalent substances are non-conductors. No charged particles that are free to move and carry current. There is an exception. Graphite. Between the layers of the lattice, delocalised electrons are able to move, When voltage is applied, these electrons are able to move freely parallel to the layers. Types of Giant Covalent Substances Diamond. High melting point, Very hard, Insoluble, Non-conductor of electricity. Graphite. High melting point. Soft and slippery. Layers can slide over each other. Insoluble. Electrical conductor. Silica (Silicon Dioxide). High melting point. Hard. Insoluble. Non-conductor of electricity. Summary: Simple Molecules and Giant Covalent Structures Simple Molecular. Low melting point. Soluble in non-polar solvents. Non-conductor of electricity. Giant Covalent. High melting point. Insoluble. Non-conductor of electricity.