on ancient Earth, nitrogen, water vapor, carbon dioxide, and methane were probably the most abundant gases in the atmosphere.
2 million years is hardly anything when considering the age of the earth. If you are considering the early earth and its atmosphere you should speak of billions of years. The inert gases (on earth) are the result of radioactive decay and build up in the atmosphere over time. Argon is (comparatively) rather abundant, Helium and Neon are fairly abundant and have found commercial applications. Xenon, Krypton, and Radon are rare but have been collected and have had an impact on human history. Health nuts use to breath pure Radon and suffer rather gruesome radiation poisoning.
Two gases that probably existed in Earth's early atmosphere are ammonia and methane. These gases were likely present in significant quantities before the atmosphere transformed into its current composition.
The first atmosphere of the earth was probably mostly hydrogen with some simple hydrides such as water vapor, methane and ammonia. Vulcanism and asteroidal bombardment eventually replaced this with an atmosphere of mostly nitrogen, with carbon dioxide and some of the inert gasses.
Earth's early atmosphere was created by gases released from volcanic activity, such as water vapor, carbon dioxide, nitrogen, and small amounts of methane. Over time, the atmosphere evolved through processes like photosynthesis by early organisms, which contributed oxygen and transformed the composition of the atmosphere to what it is today.
The first atmosphere of the earth was probably mostly hydrogen with some simple hydrides such as water vapor, methane and ammonia. Vulcanism and asteroidal bombardment eventually replaced this with an atmosphere of mostly nitrogen, with carbon dioxide and some of the inert gasses.
Oxygen (O2) was not present in early Earth's reducing atmosphere. It only became abundant in the atmosphere due to the photosynthetic activity of cyanobacteria and other early organisms.
oxygen
nitrogen
oxygen
no
photosynthsis
Hydrogen and helium
energy from the sun,lightening,earths heat triggered chemical reaction for the early gases of the earth combined
Carbon dioxide
oxygen
Methane gas
Carbon dioxide used to make up most of Earth's early atmosphere.