3.3 Chemical bonding

• Bond and bond types: ionic, covalent, metallic, van der Waals
• Bond formation in common substances: sodium chloride, water, hydrogen, diamond, graphite
• Structures of elements and compounds formed by bonding
• Relationship between bond type and physical properties
• Uses of diamond, graphite and aluminium

• identify the types of bonds formed by elements
• illustrate chemical bonding in common compounds
• distinguish structures of elements and compounds formed by bonding
• describe the relationship between bond types and the physical properties of elements and compounds
• select appropriate materials for use based on their bond type and structure
• reflect on the appropriateness of substances in day-to-day life based on their bond types and structures

“How do bond types relate to the physical properties of compounds?”

“Diamond and graphite are both pure carbon. Why is one the hardest substance known and the other soft enough to write with?”

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1. Ionic, covalent and metallic bonding
   40 min · 1 practice tasks · quiz
   Three ways atoms reach a full outer shell, and how each one shows in the properties you can measure.
2. Structure, properties and choosing materials
   40 min · 2 practice tasks · quiz
   Why diamond and graphite are so different, and how bond type decides what a material is good for.
3. Why atoms bond and how to predict the type
   40 min · 1 practice tasks · quiz
   Atoms bond to reach a full outer shell; metal plus non-metal, two non-metals, or metals together decide the route.
4. Ionic bonding in sodium chloride
   40 min · 1 practice tasks · quiz
   Sodium transfers one electron to chlorine; the ions attract, and the crystal is a giant lattice, not a molecule of NaCl.
5. Ionic formulae from electron accounting
   40 min · 1 practice tasks · quiz
   The formula of an ionic compound is the smallest ratio that lets every atom reach a full shell.
6. The ionic lattice and the properties it causes
   40 min · 1 practice tasks · quiz
   A giant lattice of ions is hard, high-melting, brittle, and conducts only when the ions can move.
7. Covalent single bonds: hydrogen, water, ammonia and methane
   40 min · 1 practice tasks · quiz
   Two non-metals share a pair of electrons; hydrogen, water, ammonia and methane show one, two, three and four single bonds.
8. Double and triple bonds: oxygen, nitrogen and carbon dioxide
   40 min · 1 practice tasks · quiz
   Atoms that still need two or three electrons share two or three pairs; carbon dioxide is two double bonds, not a giant structure.
9. Simple molecules versus giant covalent: CO2 and sand
   40 min · 1 practice tasks · quiz
   Carbon dioxide is a gas of small molecules; silicon dioxide is a giant covalent network — same family of elements, totally different properties.
10. Metallic bonding, malleability and alloys
    40 min · 1 practice tasks · quiz
    Positive ions in a sea of electrons explain conduction, bending and mixing metals into alloys such as steel and brass.
11. Intermolecular forces and the special case of water
    40 min · 1 practice tasks · quiz
    Van der Waals forces are weak attractions between molecules; hydrogen bonds make water liquid in Kenya when similar molecules are gases.
12. Testing an unknown to find the bond type
    40 min · 1 practice tasks · quiz
    Melting, solubility and conductivity as a solid and in solution form a practical sequence that identifies ionic, metallic, simple molecular and giant covalent substances.
13. Choosing diamond, graphite and aluminium in Kenya
    40 min · 1 practice tasks · quiz
    Construction drills, pencil cores, dry-cell electrodes, cooking pots and overhead power lines are chosen because of bonding and structure, not habit.
14. Bonding in everyday substances and a fair choice
    40 min · 1 practice tasks · quiz
    Salt, sugar, water, a coin, a plastic basin and sand are classified by bonding, then judged as appropriate or not for a stated use.