Which color solution is formed when sulfur dioxide gas reduces an acidic potassium dichromate solution?

Explain the following:
$(a)$ $NaCl$ is not a conductor of electricity in solid state,whereas it does conduct electricity in aqueous solution as well as in molten state.
$(b)$ Iron articles are galvanised.
$(c)$ Metals like $Na, K, Ca$ and $Mg$ are never found in their free state in nature.

Which of the following is not a metalloid?

Which of the following elements is a semiconductor?

If copper is kept open in air,it slowly loses its shining brown surface and gains a green coating. It is due to the formation of

State three reasons for the following fact: $(a)$ Magnesium is a metal. One of the reasons must be supported with a chemical equation.