Name the following:
$(a)$ $A$ metal which is preserved in kerosene.
$(b)$ $A$ lustrous coloured non-metal.
$(c)$ $A$ metal which can melt while kept on palm.
$(d)$ $A$ metal which is a poor conductor of heat.

(N/A) Sodium $(Na)$ is a highly reactive metal that reacts vigorously with oxygen and moisture in the air,so it is stored in kerosene to prevent reaction.
$(b)$ Iodine $(I_2)$ is a non-metal that possesses a characteristic lustrous appearance and is purple-black in colour.
$(c)$ Gallium $(Ga)$ and Caesium $(Cs)$ have very low melting points and melt when held in the palm of a human hand.
$(d)$ Lead $(Pb)$ and Mercury $(Hg)$ are metals that are poor conductors of heat compared to other metals like copper or silver.