The outer planets are much more massive and much lower density than the inner planets. What conditions in the disk of gas and dust that surrounded the protostar that became the sun led to the difference between the Jovian and Terrestrial planets

As explained below.

Explanation:

The outer planets are formed by gases and they have low densities than the rocky planets like earth. The protostars consists of the molecular clouds of the hydrogen and they having a critical mass tends to collide under its own gravity and thus their mass is being dominated by the presence of gases. According to the nebular hypothesis the cloud that was associated with the youthful sun was slowly rotating. As the approach of a wandering star that was in a cigar-shaped extension continued to revolve around the sun and like it to separated the material spread and slowly formed into planets. The fast and accelerating protoplanetary disk that was hot n the beginning cooled to the from the Tauri star and this formed the rocks and ice having making terrestrial planets. Formation of jovian planets was due to the distance from the sun due to the frost line and slow acceleration of the core disks

Answer volcanic outgassing;