Final answer:
The inner planets are small and rocky, while the outer planets are larger and gaseous. Terrestrial planets are composed of rock and metal with solid surfaces, whereas gas giants like Uranus and Neptune have substantial gaseous envelopes.
Step-by-step explanation:
The inner planets are small and rocky, whereas the larger, outer planets are gaseous. Planets that are more than 10 times the mass of Earth have substantial gaseous envelopes, like Uranus and Neptune, while lower-mass planets are predominately rocky in nature, like the terrestrial planets. The terrestrial planets include Mercury, Venus, Earth, and Mars, which are all relatively small worlds composed primarily of rock and metal. They have solid surfaces with geological histories recorded by features such as craters, mountains, and volcanoes. In contrast, the outer planets, including Jupiter, Saturn, Uranus, and Neptune, are much larger and composed mostly of liquids and gases, with much smaller atmospheres in proportion to their cores compared to Jupiter and Saturn.