Question

A, B, C are three elements in which B is an inert gas other than helium.With this information complete the following table.

Element	Atomic number	No. of electrons in the valence shell	Group to which the element belongs
A	Z - 1
B	Z
C	Z + 1

Also, explain the following : Ionization energy of element C is less than that of element A.

Answer 1

Element	Atomic number	No. of electrons in the valence shell	Group to which the element belongs
A	Z - 1
B	Z	8	18
C	Z + 1

Since C belongs to group 1 it has less ionization energy than A as atomic size of group 1 elements is more than that of group 17.