Answer: (highlighted in explanation)
Step-by-step explanation:
The question requires us to explain why atoms try to reach a stable state by filling their orbitals.
In general, an atom achieves stability by reaching a total of 8 electrons in its valence orbital, reaching a "stable state" similar to what is found in noble gases. We can say that when the orbital is filed with eight electrons, the atom achieved the same electronic configuration as a noble gas, or, in other words, it achieved a stable state.
Achieving stability for an atom means that no additional energy must be spent, either in forming new bonds with other atoms or emiting radiation (such as in a radioactive atom). When an atom is stable, it means that it doesn't require any transformations to stop "losing" energy.