PHYSICAL CHEM - BONDING
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What is ionic bonding?
transfer of electrons from a metal to a non-metal
What is the structure of an ionic compound?
giant ionic lattice
What forces are present in ionic compounds?
strong electrostatic forces of attraction between oppositely charged ions
What are the properties of ionic compounds?
• high melting and boiling points • conduct when molten/in solution (but don’t conduct when solid) • soluble
Why do ionic compounds have high melting and boiling points?
strong electrostatic forces between oppositely charged ions require lots of energy to overcome
Why do ionic compounds conduct when molten/in solution but not when solid?
• when solid, ions are not free to move • when molten/in solution, ions are free to move and can carry a charge through the structure
Why are ionic compounds soluble?
• water molecules are polar • charged parts of water molecules pull ions away from the lattice causing the ionic compound to dissolve
What is covalent bonding?
sharing of electrons between 2 non-metals
What is the structure of a molecular compound?
a simple molecular structure
What forces are present in molecular compounds?
• weak intermolecular forces between molecules (permanent dipole - dipole forces, van der waals forces, hydrogen bonding) • covalent bonds between atoms in a molecule (eg: I2)
What are the properties of a molecular compound?
• low melting and boiling points • don’t conduct
Why do molecular compounds have low melting and boiling points?
weak intermolecular forces between molecules require little energy to overcome
Why do molecular compounds not conduct?
no electrons free to move and carry a charge through the structure
What is diamond’s structure?
• giant covalent structure • each carbon atom bonded to 4 others
What is graphite’s structure?
• giant covalent structure • layers (graphene) • each carbon atom bonded to 3 others
What type of bonding occurs in diamond and graphite?
strong covalent bonds
What are diamond’s properties?
• high melting and boiling points • strong/hard • doesn’t conduct
Why does diamond have high melting and boiling points?
strong covalent bonds require lots of energy to overcome
What makes diamond so strong/hard?
each carbon atom is bonded to 4 others with strong covalent bonds
Why does diamond not conduct electricity?
no delocalised electrons
What are graphite’s properties?
• high melting and boiling points • soft and slippery • conducts electricity
Why does graphite have high melting and boiling points?
strong covalent bonds require lots of energy to overcome
What makes graphite soft and slippery?
layers can slide over each other as they are held together by weak intermolecular forces
Why does graphite conduct electricity?
delocalised electrons are free to move and can carry a charge through the structure