• Created by: R214116
  • Created on: 20-10-18 17:26

Ionic bonding

  • where atoms lose or gain electrons to form charged particles that are strongly attracted to one another.
  • opposite charged ions (+/-) are electrostatically attracted to one another.
  • ionic compounds have giant ionic lattices, which are closely packed in a regular lattice arrangement.
    There are very strong electrostatic forces of attraction between oppositely charged ions in all directions.

Ionic compounds have similar properties

  • high melting point & high boiling points (requires lots of energy to overcome attraction)
  • when melted, ions move freely and can carry electric current
  • dissolve easily in water, ions will move freely and can carry electric current

Compounds are made on one positively charged and one negatively charged ion so the overall charge is 0.

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Covalent Bonding

-Atoms make covalent bonds by sharing electrons with other atoms from their highest energy level so they both have a full outer shell.

Simple Molecular Substances

  • atoms form very strong covalent bonds to form small molecules of several atoms.
  • the forces of attraction between these molecules (intermolecular forces) are weak.
  • low melting & boiling points (intermolecular forces break easily)
  • most are gases or liquids at room temperature
  • don't conduct electricity

Giant Covalent Structures

  • macromolecules
  • atoms in these structures are bonded to each other by strong covalent bonds
  • high melting & boiling points
  • don't conduct electricity

Graphite - each carbon forms 3 covalent bonds - creates layers that can slide (because of weak intermolecular forces) - good conductor of heat & electricity because there is one delocalised electron per atom.

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Metallic Structures

  • metals consist of giant structures
  • have a free sea of delocalised electrons which come from the outer shell of every metal atom in the structure - so they are good conductors of heat & electricity.
  • the electrons hold atoms together in a regular structure because of strong electrostatic attraction between positive metal ions and negative electrons. This allows layers to slide so metals can be bent and shaped.

Alloys are stronger than pure metals

  • different elements have different sized atoms
  • so when mixed with another pure metal, the new metal atoms will distort the layers, making it difficult for them to slide over each other so alloys are harder
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