This element is commonly used to kill bacteria in swimming pools.
The name of this element is also used to mean a police officer.
It is the "H" in H2O (water).
Along with carbon, it is used for making steel.
Animals depend on this element in order to breathe.
The term is often used to describe the black, center part of a pencil.
It can exist as diamonds or coal.
It is often used for lifting large (and small) balloons.
Table salt is a bonding of these two elements.
ANSWERS
Chlorine
Copper
Hydrogen
Iron
Oxygen
Lead
Carbon
Helium
Sodium and chlorine