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.
1 Sometimes the drain causes air to become trapped between the lung and the chest wall. 2  This is called a pneumothorax. 3  You may become more breathless and have a sharp pain in your chest. 4  If it's a small pneumothorax, you may not need any treatment and it's likely to clear over a few days.