Final answer:
Atoms with a valence shell electron configuration of ns² belong to Group 2 on the periodic table (a). This configuration indicates two electrons in the s-orbital of the outermost shell, characteristic of Group 2 elements such as beryllium and barium.
Step-by-step explanation:
Atoms of which group in the periodic table have a valence shell electron configuration of ns²? The correct answer is Group 2. The valence shell electron configurations of the elements in Group 2 of the periodic table indeed have two electrons in the s-orbital of their outermost shell, hence an ns² configuration. This is evident in elements like beryllium (1s² 2s²) and barium (whose valence shell configuration is also ‘s²’, although its inner shells are more complex).
To show that the number of electrons in a shell equals 2n² and to clarify the number of electrons in each subshell, which is 2(2l + 1): The principal quantum number, n, represents the shell level, and each main energy level can hold up to 2n² electrons. For example, if n=2, then the second shell can have up to 2(2²) = 8 electrons. The angular momentum quantum number, l, determines the subshell and can range from 0 to n-1. For s-orbitals, where l=0, the number of electrons that can be accommodated is 2(2*0 + 1) = 2, which matches the ns² configuration of Group 2 elements.