Differentiate surface waves from body waves?

Body waves travel through the interior of the Earth. On the other hand, surface waves propagate only at the interface between two different media, like the interface between Earth and atmosphere (i.e. the surface of the Earth).

Body waves are of two types: Primary waves (also called P-waves, or pressure waves) and Secondary waves (S-waves, or shear waves).

P-waves are compression waves. They can propagate in solid or liquid material.

S-waves are shear waves. They only propagate in solid material.

By studying the trajectories of S-waves, scientists could prove that the Earth had a liquid outer core.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.