The number of protons is what defines the element. Oxygen, for example, has eight protons. However, the number of neutrons in ...

Use the animation to show students a ball model of a water molecule (H 2 O) and post the water molecule card. Explain that a water molecule has two hydrogen atoms and one oxygen atom. Ask students to ...

Microbial organisms dominate life on Earth, but tracing their early history and evolution is difficult because they rarely ...