Would the topsoil most likely be thicker in a lush,
tropical area, or in a dry area? Why?

The top soil would most likely be thicker in lush tropical area.

Explanation:

The top soil presents just above the earth's surface in the upper position of soil profile. It's thickness is 2 to 3 inches. Tropical area receives highest rainfall and direct sunlight which promotes the growth of lush vegetation that tightly holds the soil.

Dry region is devoid of vegetation. And it is free zone for air passing. With high speed wind top soil blow out from the upper surface and make surface bare. The thickness of soil in tropical area is maximum and pure.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements