What have scientists determined forms and shapes land masses here on earth?

Answer: plate tectonics

Plate tectonics is the scientific theory that describes the structure, features and movement of the Earth's crust. According to this theory, our planet's outer shell is divided into several plates which glide over the molten mantle. The interactions between these plates and the mantle shape the landmasses as well as their position on the globe.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.