which of the following gases was most likely present in earths earliest atmosphere?
a)nitrogen
b)hydrogen
c)argon
d)oxygen
To determine which gas was most likely present in Earth's earliest atmosphere, we need to understand the scientific theories regarding the formation of our planet and the evolution of its atmosphere.
The Earth is estimated to have formed approximately 4.6 billion years ago. During this early period, the planet was primarily composed of molten rocks and metals. As the Earth cooled down, volcanoes released gases from the interior, which eventually led to the development of the atmosphere.
One widely accepted theory suggests that Earth's early atmosphere was primarily composed of water vapor, nitrogen (N2), carbon dioxide (CO2), and small amounts of methane (CH4), ammonia (NH3), and sulfur dioxide (SO2). Oxygen (O2) was scarce during this time and was not a significant component of the early atmosphere.
Considering the given options, we can eliminate options C (argon) and D (oxygen) because they were not present in significant amounts during Earth's earliest atmosphere.
Option B (hydrogen) likely had a role in the early atmosphere as part of water vapor and methane. However, it was not the most abundant gas during that period.
Option A (nitrogen) is the most appropriate answer in this scenario. Nitrogen constituted a large portion of Earth's early atmosphere and has remained a major component throughout the planet's history. Nitrogen is relatively stable, non-reactive, and contributes to the overall composition of our present atmosphere.
So, the most likely gas present in Earth's earliest atmosphere is nitrogen (option A).