Question

Give the names of non-metal which are lustrous,liquid,good conductors of electricity and hardest natural substances known respectively?

Answer 1

Reflection or lustre of light of the surface is the characteristics of metal. Metal has a large number of free electrons which absorb and reflect back the light energy. Due the presence of loosely held valence electrons which are free to move in a metal structure, hence all the metals are good conductors of heat and electricity.

Complete step-by-step answer:(A) Iodine is the non-metal which show lustre property of light because by the absorption of heat energy the outermost electron of iodine gets excited and releases this energy when it comes to the normal state.
(B) Bromine is the purple-brown colour liquid at room temperature because of the high intramolecular interaction.
(C) Graphite is the non-metal which is the conductor of electricity. In graphite three valence electrons of each carbon are involved in bonding while the fourth valence electron remains free. This free electron is responsible for electric conductivity of graphite.
(D) Diamond is the non-metal which is the known hardest natural substance. In diamond each carbon atom is attached with four other carbon atoms by sigma bond. The rigid $\text{3-D}$structure of diamond makes them one of the hardest naturally occurring substances.

Note: All the halogens are gas at room temperature except bromine. Alkali metals are soft and malleable because of weak metallic bonds and large atomic size, but the density of metal is higher than non-metal.
Diamond is the other non- metal which reflects the light from its surface. Lustre is not the property of non-metal.