Why do inner planets of sun has solid surface and outer planets are largely made of gas?
A very good question indeed… the answer depends on two forces: Gravitational pull of the Sun and centrapetal force of the planets. If the planet is more closer to the sun then gravitational pull holds it in an orbit that is very much closer and also the centrapetal force that is present in the core of this mass(planet) tends to draw the molecules closer to the core and hereby compressing/condensing the entire mass.As both these forces are proportional to each other it can be observed that planets that are closer to the sun are solid while those further away tend to be made of gases.
