Ch - 3 (Giant Structures & Metallic Bonding )
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What are the examples of giant covalent structures?
• Diamond • Graphite
What is the structure of a diamond?
• Each carbon atom bonds with 4 other carbon atoms • Forms tetrahedron • Very strong • No intermolecular forces
What is the structure of graphite?
• Each carbon atom is bonded to 3 other carbon atoms • Forms layers of hexagon • Weak intermolecular foxes.
Properties of diamond?
• Doesn’t conduct electricity (No free charged ion) • High m.p. (Strong covalent bonds, needs more energy) • Extremely hard and dense
What is the use of diamond?
• Jewellery • cutting tools
Properties of graphite?
• Weak intermolecular forces that makes layers slide and slippery • conducts electricity • High m.p. • less dense than diamond.
What are the uses of graphite?
• Pencils • Industrial lubricants • Used for electrodes and electrolysis.
How is the structure of silicon dioxide?
• Macromolecular (Sand and quartz) • Each oxygen covalently bonds with 2 silicon atoms • Each silicon atom covalently bonds with 4 oxygen atoms • Tetrahedron
What are the properties of silicon dioxide?
• No intermolecular forces so same property as diamond. • Hard • High b.p. • Insoluble in water • Does not conduct electricity • Cheap (Sandpaper)
What is metallic bonding?
Metal bonds are held together in a giant metallic lattice
What happens to the atoms of metallic bonding?
• Lose electrons from outer shell and become positively charged ions. • Delocalised electrons
How do the electrons flow?
Like a ‘sea of electrons’
What are the properties of metals?
• High m.p. & b.p. • Conduct electricity • Malleable and ductile
Why do metals have High m.p. & b.p.?
• Strong metallic bonding between positive ions and delocalised electrons • Lot of heat required
Why do metals conduct electricity?
• Delocalised electrons
Why are metals malleable and ductile?
• Layers of positive ions can slide over each other. • Strong but flexible.