Final answer:
Nitrogen is the atmospheric gas molecule that comprises the largest percent of the air we breathe, making up approximately 78% of the Earth's atmosphere.
Step-by-step explanation:
The atmospheric gas molecule that makes up the largest percent of the air that we breathe is nitrogen (N₂). Our air is essentially a gas-gas solution where approximately 78% of the atmosphere consists of nitrogen, making it the most abundant gas in the Earth's atmosphere. Oxygen (O₂), which is crucial for life and various processes like combustion and respiration, comes next, making up about 21% of the atmosphere. Despite the vastness and complexity of the atmosphere's composition, these two gases, nitrogen and oxygen, constitute nearly 99% of the air's composition.