In general, atoms with incomplete valence shells tend to be more reactive and likely to participate in chemical reactions. In the case you mentioned, the atom with two electrons in its valence shell is likely to be an insulator, while the atom with seven electrons in its valence shell is likely to be a conductor.
Insulators are materials that do not conduct electricity easily because their valence shells are almost completely filled. The presence of only two electrons in the valence shell indicates that the first atom is closer to having a stable, full valence shell, making it less likely to readily participate in electron flow and conduct electricity.
On the other hand, conductors are materials that readily allow the flow of electric current due to the presence of loosely held or free electrons in their valence shells. The atom with seven electrons in its valence shell is closer to achieving a stable, full valence shell, but it still has room for additional electrons. This allows for the possibility of easy movement of electrons and makes it more likely to conduct electricity.
It's important to note that the behavior of specific atoms and materials can vary depending on their atomic structure, bonding, and other factors. The above explanation provides a general understanding based on the given information, but there may be exceptions and variations in real-world scenarios.