What you learnt at school and in some books is false! There aren't on one side
telluric planets (as the Earth) and of the other one the giant planets (as
Jupiter) but all the planets are telluric. Indeed, the planets which one calls
in twists "gas giants" contain a solid core, that we can't see because it is
hidden by a thick atmosphere. For example, it's written in the French Pierre
Kohler's very serious book "The Earth and Celestial bodies" edited by Hachette
Encyclopedy page 138 that the centre of Jupiter is occupied by a sphere of
solid hydrogen about 92000 km in diameter. So Jupiter is not a gazeuze planet
of diameter 142700 km but a telluric planet of diameter 92000 km recovered by a
thick opaque atmosphere of a height of 142700 - 92000 = 50700 km, counts that
it is necessary to divide by two because the thickness is counted in both
diametrically opposite directions, what gives an atmospheric thickness of 25350
km. There is a similar structure for Saturn, Uranus and Neptune.