Noble metals: These metals are less reactive. Of course, they react in liquid or powder forms. But in general, they do not corrode and rust on exposure to air. They are soft and can be easily moulded into different forms. They are quite expensive due to above properties and are used in jewellery, coin making etc. Ex- Gold, platinum, silver.
Metals characteristics and properties
Hardness.– Allows a metal to resist penetration. The harder the metal the less likely it is to change in shape. Hardness can be increased by hardening or heat treating.
Brittleness.- Makes a metal break easily. Certain kinds of cast iron are brittle and break when dropped. Hardness and brittleness are closely related since hard metals are more brittle than soft metals.
Malleability– Allows a metal to be hammered or rolled out into thin sheets without breaking or cracking.
Ductility– Allows a metal to be drawn out into thin wires without breaking. Copper is very ductile and therefore makes very good wire.
Elasticity– Allows metals to return to its original shape after bending. Steel used in making springs is a good example.
Fusibility-Allows metals to become liquid easily and join with other metals to form an alloy.
Machinability-Some of these are the rate at which the material can be removed in machining, the chip, the amount of tool wear, and the kind of surface finish.