The atmosphere can be described in terms of three physical components, dry gases, water vapor, and solid particles. The atmosphere is chemically stratified and 99% of the mass in the atmosphere in contained with in the troposphere and stratosphere alone. This means that 99% of the mass is contained within the inner 10% of the atmosphere. The skewed distribution is due to waning gravitational effects with distance from earth, combined with linearly decreasing atmospheric pressures acting on the gases. Therefore, most discussion about mass budgets, and the chemical make up of the atmosphere focus upon the inner two spheres.
Air itself may be described as a mixture of dry gases, water vapor, plus or minus solid particles and its composition changes with distance from earth. Nitrogen, oxygen, argon, and carbon dioxide are 99.9% of the natural dry gas composition of air. Beyond the Stratosphere, the gases are distributed according to their densities creating stratified molecular layers with the heavier molecules nearer to Earth. The stratification remains undisturbed in general because it resides in the static upper levels of the atmosphere, rarely mixing beyond the pausal zones. Solar radiation interacts with the chemical strata, producing charged particles by stripping electrons. Ozone is a byproduct of electron stripping, which allows O2 to become O3. Fortunately, this occurs only high in the atmosphere, because ozone in high concentrations is quite hazardous.
Oxygen is a colorless, odorless gas first discovered by Joseph Priestly, an English Clergymen. Oxygen is essential to all air breathing animals, respiring plants, and accounts for 89% by weight of all the water and air within Earths planet system. Oxygen is highly reactive due to its electron valence. Because oxygen is highly abundant and very reactive many oxides form on Earth and in its atmosphere. Thats why airborne pollutants cause such problems, we emit excess carbon, nitrogen, and sulfur, into the air which oxidizes and remains suspended in the air poisoning the biosphere.
Carbon dioxide is a colorless, odorless gas that is noxious to animals, but necessary to plants. Plants use carbon dioxide, water, and energy derived from the sun to produce sugar. This process is photosynthesis. Carbon dioxide may be considered a major pollutant though, when human activities put enough carbon into the atmosphere to cause immediate health hazards, local climate changes, and possible long term climatic effects. Carbon monoxide is a byproduct of two major consumer products: 1) cement manufacture, and 2) fossil fuel consumption. Because carbon monoxide can reflect short wave radiation emitted from earth towards space, it can cause increases in local temperatures. Scientists also theorize that if catastrophic concentrations of carbon dioxide accumulate in the atmosphere our global temperatures will rise causing catastrophic unrecoverable global climate changes. Opposing scientists argue that the carbonate cycle would buffer Earths atmosphere by precipitating limestone in the worlds oceans, seas, and lakes.