I believe that Isotopes of elements have different atomic masses. So A) Atomic masses.
During diffusion substances move from the denser medium (meaning where there is more of the substance) to less dense medium (meaning where there is less of the substance).
Answer:
The atmosphere, I believe.
Explanation:
<span>increase while moving left to right within a period and increase while moving upward within a group. </span>
<span>Gravel settled at the bottom and clay settled at the top.</span>
