Metals can be classified according to their chemical activity into three groups which are very active metals, less active metals, and inactive metals. The high reactivity of active metals makes them useful in a...
The electric conductivity The substances can be classified according to the electric conductivity into good conductors of electricity and bad conductors of electricity, The electrical conductivity is the ability of a material to carry...
Hardness of materials Some solid substances are soft at room temperature such as the rubber, and some solid substances need heat to become soft and easy to be shaped such as the metals, and...
The movement of electrons The electrons are negatively (- ve) charged particles, They revolve around the nucleus with very high speed, The electron has a negligible mass relative to that of the proton or...
