Rusting of an article made up of iron is called

Non-metals are usually poor conductors of heat and electricity. They are non-lustrous,non-sonorous,non-malleable,and are coloured.
$(a)$ Name a lustrous non-metal.
$(b)$ Name a non-metal which exists as a liquid at room temperature.
$(c)$ The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.
$(d)$ Name a non-metal which is known to form the largest number of compounds.
$(e)$ Name a non-metal other than carbon which shows allotropy.
$(f)$ Name a non-metal which is required for combustion.

On heating,calcium carbonate gets converted into calcium oxide and carbon dioxide.
$(a)$ Is this a physical or a chemical change?
$(b)$ Can you prepare one acidic and one basic solution by using the products formed in the above process? If so,write the chemical equations involved.

When a bar magnet is brought closer to a mixture of iron filings and sulphur powder,iron particles stick to the magnet,whereas in the case of iron sulphide,no change is observed. When a mixture of iron and sulphur is added to carbon disulphide,sulphur dissolves,whereas in the case of iron sulphide,no change is observed. Justify the statement that the properties of a compound are different from its constituents,while a mixture shows the properties of its constituent elements using the example of iron and sulphur.

Two substances,$A$ and $B$,were made to react to form a third substance,$A_2B$,according to the following reaction: $2A + B \to A_2B$. Which of the following statements concerning this reaction are incorrect?
$(i)$ The product $A_2B$ shows the properties of substances $A$ and $B$.
$(ii)$ The product will always have a fixed composition.
$(iii)$ The product so formed cannot be classified as a compound.
$(iv)$ The product so formed is an element.

State whether the following statement is true or false:
$A$ compound is a substance composed of two or more elements,chemically combined with one another in a fixed proportion.