(a) Complete the table.

Atomic No	Element	Electronic configuration	Select element of the same group
11	Sodium	……………	(Ca/N/K)
15	Phosphorus	……………	(Al/N/C)
16	Sulphur	……………	(F/Cl/O)
9	Fluorine	……………	(Ca/Cl/K)

(b) Classify the elements given in the table as metals and non-metals.

(c) To which group does sodium belong? Why is Hydrogen not considered while describing the elements of this group?

(a) The completed table is given below:

(b)

(c) Sodium belongs to group 1.
Position of hydrogen is not satisfactory. Hydrogen atom is very small in size and therefore many of its properties are different from group 1 elements (alkali metals). It is a gas at room temperature, while other elements of group 1 are solid metals. Secondly, it does not readily form cations, in most compounds, whereas group 1 metals readily form cations and form only ionic bonds. Due to these reasons Hydrogen is not considered while describing the elements of group 1.