When is a compound said to be pure?

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.

Differentiate between an element and a compound. Categorize the following substances into elements and compounds: Sodium chloride,Iodine,Water,$24$ carat gold,Oxygen gas,Carbon.

What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?

An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?

State whether the following statement is true or false:
Non-metals are lustrous and good conductors of heat and electricity.