bonding and properties

• Ionic Bonding

  -the electrostatic attraction formed between the oppositely charged ions

  -transfer of electrons from a metal to a non-metal

  -metals lose electrons from their valence shell forming +ve charged cations

  -non-metals gain electrons forming -ve charged anions
• Covalent Bonding

  -the sharing of electrons between two non metals

  -electrostatic attraction between nuclei of two atoms and the bonding electrons
• Dative covalent bonding

  Covalent bonding in which both electrons in the bond come from one of the atoms in the bond
• Metallic Bonding

  -the attraction between delocalised electrons and positive ions

  -packed together in lattice structures

  -when e- are delocalised, metal atoms become +ve charged

  -+ve charged repel each other keeping the lattice arranged in place

  -very strong forces between the +ve metal ions and the sea of delocalised e-
• Ionic lattice structures

  -crystalline lattice

  -regular repeated arrangement

  -type of lattice formed depends on sizes of -ve and +ions
• covalent lattice structures

  -can be arranged in simple molecular (eg. iodine, buckminsterfullerene) or giant molecular lattices (eg. graphite and diamond)
• metallic lattice structures

  -often packed in hexagonal layers or in a cubic arrangement

  -if other atoms are added then it creates alloys

  -alloys are much stronger than pure metals
• metallic lattice structures - increase strength

  -increasing the number of delocalised electrons per metal atom

  -increasing the =ve charges on the metal centres

  -decreasing the size of the metal ions
• metallic bonding properties - high melting and boiling point

  -many strong metallic bonds so large amounts of heat energy are needed to overcome forces and break these bonds
• metallic bonding properties - good conductors of electricity and heat

  -good conductors of heat - free electrons that can carry the charge

  -good conductors of electricity - e- entering one end of the metal cause a delocalised e- to displace itself from the other end, hence e- can flow so electricity is conducted
• metallic bonding properties - malleable and ductile

  -layers of +ve ions can easily slide over one another and take up different positions

  -doesn't disrupt the bonding as e- are valence e- do not belong to any particular metal so they can move around

  maintaining the force

  -metallic bonds are not broken but are strong and flexible
• effects of bonding and structure on physical properties - ionic bonding

  -strong but brittle

  -high melting and boiling points - strong electrostatic forces of attraction

  -are soluble in water - can form ion-dipole bonds

  -can conduct electricity when molten or in solution - ions are free to move around
• effects of bonding and structure on physical properties - metallic bonding

  -malleable - metal layers can slide

  -strong and hard

  -high melting and boiling points

  -pure metals insoluble in water

  -conduct electricity when in solid or liquid state
• effects of bonding and structure on physical properties - covalent bonding - simple covalent lattice

  -simple covalent lattices have low melting and boiling points - weak intermolecular forces

  -are insoluble with water - unless they are polar and can form hydrogen bonds

  -do not conduct electricity in solid or liquid state
• effects of bonding and structure on physical properties - covalent bonding - giant covalent lattice

  -large number of covalent bonds so lots of energy required to overcome them

  -can be hard or soft - granite is soft as the forces between layers are weak. diamond is very hard as it is hard to break their 3d network of covalent bonds

  -most are insoluble in water

  -most do not conduct electricity except graphite - delocalised electrons between carbon layers.