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.

Explanation

(i) Valency of group 1 elements = 1
Valency of oxygen = 2
Oxides of group 1 elements :
Formula of the oxides of group 1 is `M_(2)O`, where M is the group 1 element and O is oxygen.
(ii) Valency of group 13 elements = 3
Valency of halogens = 1
Halides of group 13 elements :
Formula of the halides of group 13 is `MX_(3)`, where M is the group 13 element and X is halogen.
(iii) Valency of group 2 elements = 2
Valency of group 16 elements = 2
Compounds of group 2 and group 16 elements :
Formula of the compounds of group 2 and 16 is MN, where M is the group 2 element and
N is the group 16 element.