Sodium and chlorine are poisonous substances but sodium chloride is edible.

1. Sodium chloride is a compound of sodium and chlorine.
2. Physical and chemical properties of constituent elements are not retained in a compound (i.e. properties of sodium and chlorine are different as compared to sodium chloride.)
3. When chemically bonded, these two poisonous substances form a compound sodium chloride so safe that we eat it every day.