Give an example of monovalent and trivalent element in group III.

The equivalent weight of a certain trivalent element is 20. molecular weight of its oxide is

Give one example of a combination reaction in which an element combines with a compound to give you a new compound.

The valency of any element of group 18 is

Give one example each of polyatomic element and polyatomic ion .

The group reagent for group III is:

Write some example of the Elements ?

Based on the group valency of elements state the formula for the following giving justification for each : (i) Oxides of 1^(st) group elements, (ii) Halides of the elements of group 13, and (iii) Compounds formed when an element of group 2 combines with, an element of group 16.