As the elements have the maximum number of electrons in their valence shells (thereby achieving stable duplet and octet configurations), they do not have any tendency to combine with other elements.
Helium, Neon, Radon and Argon have zero valency because they have their outer shell completely filled and are chemically inert gas. Was this answer helpful
The solar system is made up of the sun and everything that orbits around it, including planets, moons, asteroids, comets and meteoroids. It extends from the sun, called Sol by the ancient Romans, and goes past the four inner planets, through the Asteroid Belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the teardrop-shaped heliopause. Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun. Beyond the heliopause lies the giant, spherical Oort Cloud, which is thought to surround the solar system.
