Answer: We can say that when the valence shell of an atom reaches eight electrons, the atom achieved the same electronic configuration as a noble gas, or, in other words, it achieved a stable state.
Step-by-step explanation:
The question requires us to explain why an atom "wants" to have a filled orbital.
In general, an atom achieves stability by reaching a total of 8 electrons in its valence orbital, reaching a state similar to what is found in noble gases. This stability is reached by bonding with other atoms, either "donating" or "receiving" electrons through an ionic bond, or "sharing" electrons through a covalent bond. We can say that when the valence shell of an atom reaches 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 by forming bonds or emiting radiation.