Q8 of 27 Page 1

Based on the group valency of elements write the molecular formula of the following compounds giving justification for each:

(i) Oxide of first group elements


(ii) Halide of the elements of group thirteen, and


(iii) Compound formed when an element, A of group 2 combines with an element, B of group seventeen.


i. A2O – Valency of group one is 1 and of oxygen is 2


element.png


The formula for group 1 oxides is A2O, where A is the group 1 element and O is oxygen.


ii. AX3 – Valency of group 13 is 3 and of halogen is 1


element.png


Formula for the halides of group 13 is AX3 where A is the group 13 element and X is the halogen.


iii. AB2- Valency of element A of group 2 is 2 and that of element B of group seventeen is 1.


element.png


A of group 2 has a valency of 2 and it combines with an element, B of group seventeen which has the valency 1. Therefore the formula is AB2


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