How does the way in which the solar system formed explain the orbits, sizes, and compositions of the planets?

DUE TO GRAVITATIONAL COLLAPSE SOLAR SYSTEM IS FORMED , ORBITS ARE CURVED TRAJECTORIES AND SIZE AND COMPOSTION OF PLANET ARE VERY UNIQUE AND COMPOSED OF ROCKS AND METALS and evolution of solar system has began 4.5 billion years ago,due to gravitational collapse of a small particle from a giant cloud.

it's c. elements are placed in rows based on how may valencies electrons have.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.