Answer
Please see the work below.
Work Step by Step
The total number of electrons in the valence shell is equal to the group number for the representative elements.
a) $[Ne]3s^{1}$.
In this element, the valence shell is the third shell and it contains 1 electron; hence it is a group 1A element.
b) $[Ne]3s^{2}3p^{3}$
In this element, the valence shell is the third shell with 3s and 3p orbitals and it contains 5 electrons; hence it is a group 5A element.
c) $[Ne]3s^{2}3p^{6}$.
In this element, the valence shell is the third shell with 3s and 3p orbitals and it contains 8 electrons; hence it is a group 8A element.
d) $[Ar]4s^{2}3d^{8}$.
In this element, the valence shell is the fourth shell with 4s orbital and the penultimate shell is the 3d orbital with 8 electrons. The sum of electrons in the valence shell and the penultimate shell is 10. Hence it is group 10 or 8B. For transition elements, if the sum of electrons in the valence shell and the penultimate shell is 8,9 or 10, then the elements belong to the group 8B.
