Structure and Properties

Structure and Properties

1. Giant Ionic Structures

   • High melting points and are all solids at room temperature.
   • Strong Electrostatic forces between negatively charged Ions hold the structure together.
   • A lot of energy needed to break the bonds
   • When melted or dissolved in a solution the Ions are free to move therefore can conduct charge

2. Simple Molecules

   • Atoms in a molecule are held together by strong covalent bonds and bonds act only between atoms within a molecule.
     • Simple molecules have little attraction to eachother
   • Have relatively low melting and boiling points and no overall charge so do not conduct electrical charge.
   • Intermolecular forces
     • Weaker means easier to melt or boil

3. Giant covalent structures

   • Atoms of some elements can form several covalent bonds and therefore giant covalent structures.
     • Huge levels of energy required to break the lattice so high melting points
   • Diamond is a form of carbon with a 3 dimensional structure and every carbon atom is covalently bonded to four other carbon atoms which makes diamond hard and transparent.
     • Silicon Dioxide has a similar structure
   • Graphite is a form of carbon where the carbon is covalently bonded to 3 other carbon atoms in giant flat 2D layers. No bonds between the layers so they slide over each other and graphite is slippery and grey.
     • Has delocalised electrons which allow graphite to conduct heat and electronic charge.

4. The fullerenes

   • Large molecules formed from hexagonal rings of carbon atoms. The rings join together to form cage like structures with different numbers of carbon atoms, some of which are nano-sized. Scientists have found many uses for fullerenes including drug delivery into ther body, lubricants, catalysts and reinforcing materials

5. Giant metallic structures

   • Metal atoms are arranged in layers and when a force is aplied the layers can slide over each other which is why pure metals are malleable.
   • Alloys are mixtures of metals with other atoms such as carbon which distort the shape of the atoms in the metal therefore the alloy is much harder.
   • Shape memory alloys can be bent or deformed into a different shape and return to original shape when heated.
     • Nitinol dental braces
   • Delocalised electrons

6. Properties of Polymers

   • properties of a polymer depend on the monomers used to make it, and the conditions and catalyst used in the reactions
     • LDPE AND HDPE are made using different catalysts and different reaction conditions. HDPE has a higher softening temperature and is stronger than LDPE
   • Polyethene is an example of a thermosoftening it is made up of individual polymer chains tangled together and can be heated and moulded and remoulded
   • Thermosetting polymers do not melt do not melt or soften when heated due to cross links.

7. Nanoscience

   • The study of small particles between 1 and 100 nanometres in size
     • Could have harmful effects on health and the environment
   • behave differently from the materials they are made from
   • Used as sensors, catalysts,cosmetics,construction materials. Small size and large surface area very useful and makes them an excellent material and catalyst.