And the planets only have attraction?

Notice that in the solar system, the larger planets are distant from the huge sun and near the sun you can realize that the planets are the smaller possible, mercury is the smallest planet of the solar system so the attraction is bigger for who is smaller the bigger planets are kind of far maybe there are also repulsion, planets collide? If the attraction was like explained probably planets would collide. Rute Bezerra de Menezes Gondim