Thursday, 10 December 2015

Lecture 1 – Introduction & Properties of Metals

ACKNOWLEDGEMENT:

Figure (respectively)
Source of Figure
Figure 1a
http://chemistry-igcse1.weebly.com
Figure 1b
http://wurstwisdom.com
Figure 2
www.ausetute.com.au
Figure 3
http://www.gcse.com
Figure 4
http://sites.google.com








Metals:

Metals are arranged in Group I, II, III and the Transition element block of the Periodic Table. In this chapter, the Transition metals and Group III metals will be discussed, as Group I and II metals are relatively soft and differ in terms of physical properties.

Physical properties of Metals:
  1. Metals are solids with high melting and boiling points. (an exception is mercury, which is a liquid at R.T.P)
  2. Metals have high densities.
  3. Metals are good conductors of heat and electricity.
  4. Metals are ductile; means that they can be drawn into wires.
  5. Metals are malleable; means that they can be made into sheets.
  6. Some metals are magnetic.
Physical structure of metal lattice:

Atoms in metals are regularly arranged in 3-dimensional rows and columns as positive ions, with their valence electron moving independently with in the body of the metal lattice. The ions are packed together and can not move.

Figure 1a:

 Figure 1b: 3D structure
Table 1 shows how the structure of the metal lattice contribute to each of the physical property discussed above.

Table 1:

Physical Property
Reason
Pictorial Explanation
High Melting and Boiling Points
The ions are arranged in regular pattern with large interatomic forces of attraction between them. Therefore, a large amount of heat is required to overcome these forces and melt the solid to liquid and even greater to boil it.
High Densities
The ions are closely arranged to each other with less or no space between them, thus contributing to high densities. 
Density = mass/Volume

 
Good conductor of Electricity
Metallic ions are surrounded in a sea of free electrons. When a potential difference is applied across the metal lattice, these electrons, being negative in nature, travel to  the positive end of the applied potential. This unidirectional movement of all free electrons, enable metals to conduct electricity.


Good conductors of heat
Heat in metals travel across the lattice in 2 ways:
i.                    The free electrons carry heat from the hot end to the cold end and they continue to do this until equilibrium is achieved and the entire body of the metal is uniformly heated. This is the faster mode of heat transmission via the metallic lattice
ii.                  The slower heat transmission occurs by the vibration of the ions near the heated end of the lattice. They vibrate to pass on the heat to the adjacent ions and so on until the vibration spreads through the lattice.

   

Metals are ductile and malleable
The metallic ions are packed together with large interatomic forces in the form of layers. These forces are large but not rigid, therefore if a large force is applied in the direction of the layers; the layers can slide on top of one other. This makes them ductile and malleable.