molecular energy level. (physical chemistry). One of the states of motion of nuclei and electrons in a molecule, having a definite energy, which is allowed by quantum mechanics.1  Facebook.olecular energy level. (physical chemistry). One of the states of motion of nuclei and electrons in a molecule, having a definite energy, which is allowed by quantum mechanics. 1  Facebook.
Air first enters your body through your nose or mouth, which wets and warms the air. (Cold, dry air can irritate your lungs.) The air then travels through your voice box and down your windpipe. The windpipe splits into two bronchial tubes that enter your lungs.
The lungs are like a pair of balloons inside the chest that fill up with air and then relax to let air leave the body. When a blockage occurs in the airway so the lung cannot fill up with air or if a hole or weakened place develops in the lung allowing air to escape, the lung can collapse like a balloon that has lost its air.