Bonding
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What are the properties of covalent bonds
Low melting and boiling point due to weak intermolecular forces These intermolecular forces are increased with molecular size e.g. there are bigger forces between C2H6 than CH4
Why do covalent bonds have a shared pair of electrons
To gain a noble gas configuration
What is an ionic bond
The type of bonding that occurs between a metal and a non-metal An electrostatic attraction between type oppositely charged ions
What does the electrostatic attraction cause
The formation of +ve and -ve ions with stable noble gas configurations
Properties of ionic bonding
Ionic lattices - ionic solids are often crystalline The ions are arranged in a giant 3D lattice pf alternating +ve and -ve ions Strong electrostatic attraction between the anions and cations, this causes high melting and boiling points
What is metallic bonding
The bonding found between two metals
What is a metallic bond
Electrostatic attraction between metals ions and a sea of delocalised electrons
Why are metallic bonds good conductors
The electrons are free to move
Why do metallically bonded compounds have high melting and boiling points
Because the electrostatic attraction between positive metal ions and delocalised electrons is strong
How does electrostatic attraction change is the metal becomes more malleable
The electrostatic attraction weakens
What is the difference between ionic and covalent bonds?
Ionic bonds are crystalline solids whereas covalent bonds are liquids or gases Ionic has high b.p./m.p. and covalent has low b.p./m.p. Ionic bonds are soluble in water and covalent bonds aren’t Ionic bonds aren’t soluble in organic solvent but covalent bonds are Ionic bonds conduct electricity in molten or solution state whereas covalent bonds do not
Why can ionic bonds conduct electricity in molten or solution state
Because the ions are free to move and carry charge
Why can’t covalent bonds conduct electricity
There are no charged particles to carry charge
Define allotropy
The substance has more than one form that can occur in a physical state
Examples of carbon allotropes
Diamond, graphite, graphene, buckminsterfullerene (C60)
Describe the properties of graphite
Electrically conductive Black, opaque, shiny density 2.25g/cm3
Describe the properties of diamond
Electrical insulator Transparent, shiny, sparkles Hardest known substance 3.52g/cm3
Describe bonding of graphite
Layered structure Hexagonal patterns within layers Strong bonds within layer Weak forces between layers Spare electron per carbon atoms leads to electrical conductivity between layers
Why is graphite a good lubricant
The weak forces between layers
Describe properties and structure of diamond
Tetrahedral arrangement Each C atom bonds with four others Strong bonds with no spare electron making it a good insulator Shape of diamond makes it very hard
What structures do graphite and diamond have
Giant structures
Describe the properties of silicon (IV) oxide
High mpt and bpt Isn’t electrically conductive Hard but not as hard as diamond which is 8 times harder
How many types of bonding are there?
3 - metallic, ionic, covalent
Why do giant ionic lattices have a high melting and boiling point
Strong electrostatic forces of attraction between oppositely-charged ions require a lot of energy to break