All of the noble gases have this fact in common: a. they are all radioactive. b. their outer shells are full of electrons. c. they will react chemically with other elements quite easily. d. they are all very common and can be found easily in nature.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.