Question

Based on the group valency of elements state the formula for the following giving justification for each:

(i) Oxides of 1st group elements.

(ii) Halides of the elements of group 13.

(iii) Compounds formed when an element of group 2 combines with an element of group 16.

Answer 1

The elements in a group tend to have similar physical and chemical properties because of their similar outer shell electron structure.

1. Valency of first group elements is 1 and that of oxygen is 2. Hence, oxide of first group is $X_{2}O$.

Eg; H O

1 2 (Criss cross)

$H_{2}O$ is the oxide.

2. Group 13 has a valency of 3 and that of halogen is 1. Hence, halide of group 13 is $M{X}_3$

Eg; B Cl

3 1 (Criss cross)

$BC{l}_3$ is the halide.

3. The valency of the Group 2 elements is +2 and that of Group 16 elements is -2. Group 2 loses electrons and group 16 accepts electrons. Hence, compounds formed are $MY.$

Eg; Mg O

2 2 (Criss cross)

$MgO$ is the compound.