(a) Name the three classes in which elements are classified. Which was the first metal used by man?

(b) Name the metal and non-metal present in abundance in the earth crust.

Give the importance of the following in living beings:

(a) Nitrogen

(b) Hydrogen

(c) Carbon

State the position of the following in the periodic table:

(a) Alkali metals

(b) Alkaline earth metals

(c) Halogens

(d) Aluminum

Name:

(a) a liquid non-metal

(b) two metalloids

(c) a metal which do not corrode easily

(d) two metals which react with cold water

(e) a non-metal which can form a positive ion.

(f) a non-metal which shows reducing property.