CHARACTERISTICS:
- high density
- high melting points
- high boiling points
- good conductors of heat and electricity
- high malleability and ductility
- weak and soft
** to explain malleability and ductility of pure metal
- metals are composed of identical atoms.
- They are packed together as close as possible and arranged orderly from one layer to another to form a three-dimensional crystal lattice.
- When a force is applied,the layers of atoms start to slide over each other.
- After slipping,the atoms settle into new positions and the metal structure is restored.
- The ability of layers of atoms sliding easily makes metals malleable and ductile. Thus,metals can be hammered into different shapes or pulled into a wire.
ALLOY
-material that contains mixture of elements and has metallic properties.
-most alloys are mixtures of metals. But,it may also contains mixtures of metals and non metals.
What are the purposes of making alloy?
1. improving the appearance of a metal
-alloying helps to prevent formation of the oxide layer and
enables the metal to keep its surface shiny.
2. Increasing the strength and hardness of a metal
-The new element added to the pure metal disrupt the orderly
arrangement of atoms of the lattice of pure metal. This prevent
the layers of atoms from slipping over each other and hence
makes the pure metal stronger and harder.
3. Increasing resistance to corrosion of a metal.
-Unreactive metals such as gold does not combine with oxygen to
form oxides. Hence it does not corrode readily.
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