[DOC] [TLE] Atmosphere - The Ozone Hole [PAR] Two gases make up the bulk of the earth's atmosphere: nitrogen ( ), which comprises 78% of the atmosphere, and oxygen ( ), which accounts for 21%. Various trace gases make up the remainder. Based on temperature, the atmosphere is divided into four layers: the troposphere, stratosphere, mesosphere, and thermosphere. [DOC] [TLE] Atmosphere of Earth - Wikipedia [PAR] By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. [DOC] [TLE] Molecules of the Atmosphere Composition of the Atmosphere [PAR] The present atmosphere consists mainly of molecular nitrogen (N2) and 
molecular ... Over time, the excess oxygen has built up so that it is now makes up 
nearly 20% ... is present as 5.0 x 102/109 or only 0.00000050, 0.000050% of all 
gas particles. ... Molecular nitrogen makes up 78% of the gases in the 
atmosphere. [DOC] [TLE] PDC Test - Atmospheric Observations - Certification & Training ... [PAR] ... of protons, electrons and neutrons, as well as the orbital patterns displayed 
around their nuclei. ... An atom of nitrogen has seven protons, while oxygen has 
eight. ... The gas that makes up about 78 percent of the earth's atmosphere by ... c
) causes poisonous reactions d) is found only in a liquid state 20. All atoms have 
the... [DOC] [TLE] Why nitrogen is 78% in the atmosphere? - Quora [PAR] The answer lies mostly in three facts: 1. nitrogen is volatile in most of its forms. 2. 
it is unreactive ... N2 gas is made up of N triple bond N. Since there is a triple 
bond in the diatomic ... Nitrogen only reacts with oxygen in car engines. ... is 
wrong - the level of nitrogen in air actually fluctuates but broadly is stabilized 
around that... [DOC] [TLE] Composition of Our Atmosphere - Geography For Kids - By KidsGeo ... [PAR] The most abundant gases found in our atmosphere are nitrogen and oxygen. 
Nitrogen makes up around 78% of the total atmosphere, while oxygen makes up
... [DOC] [TLE] What gases make up the Earth's atmosphere? | Reference.com [PAR] The Earth's atmosphere is primarily made up of nitrogen, oxygen and argon, but it 
... The most abundant gases in the atmosphere are nitrogen at 78 percent and ... 
while the trace gases methane, neon and helium make up around one-tenth of... [DOC] [TLE] What are the layers of the atmosphere and the gases in each layer ... [PAR] Jun 14, 2014 ... The exosphere is also made up of the earth's lightest gases, which are mostly 
hydrogen, ... density by assuming the air is dry, giving only negligible errors in the 
results. ... Primarily composed up of 78% nitrogen and 21% oxygen. ... This layer 
is around 31 miles and holds 19% of the atmosphere's gases. [DOC] [TLE] Atmosphere | Atmospheric Gases | Aerosols | Greenhouse Gases [PAR] Air is a mixture of gases and aerosols that composes the atmosphere ... The main 
gases are nitrogen and oxygen, which make up 78% and 21% of the ... to 
ordinary atmosphere pressure at ground level, it would occupy a layer only 3 mm 
thick. ... During the 20th century other man-made processes have put completely 
new... [DOC] [TLE] What Is the Chemical Composition of Air? - Chemistry - About.com [PAR] Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, 
oxygen, water vapor, argon, and carbon dioxide. Several other compounds also 
are... [DOC] [TLE] Evolution of the Atmosphere [PAR] The first atmosphere was formed by outgassing of gases trapped in the interior ... 
by nitrogen, but there was certainly no oxygen in the early atmosphere. ... how 
photosynthesis could have led to maintenance of the ~20% present-day level of 
O2. ... could only have begun once the level of oxygen had built up to

Question: Nitrogen makes up around 78% of the atmosphere; this gas, only about 20%
Answer: oxygen