ATPL-EASA-MC01Atmosb

Sunset over the Indian Ocean, viewed form the International Space Station The oranges and yellows show the troposphere The pink and white is the stratosphere Above Abov e that are the mesosphere, thermosphere, ionosphere and exosphere, eventually eve ntually merging to the black of space.

!" #itrogen, $%" oxygen, &.'" Argon That(s ''.'" ''.'" of the atmosphere atmosphere

)ife needs nitrogen compounds. Air is !" nitrogen in the form of the molecule #$. #itrogen in this form is unavailable to most organisms, but the molecule is highly inert. It takes a lot of energy to separate the atoms so that they can combine to form the *fixed+ nitrogen, i.e. nitrogen in compounds such as nitrates #O-/, ammonia #0-/ and urea #0$/$1O/

The enormous energy of lightning separates the nitrogen atoms so they can combine with oxygen to form nitrogen oxides. These dissolve in rain, producing nitrates. #itrogen can also be *fixed+ by biological action and industrial

fixation.

Oxygen was discovered by @ilhelm Scheele in Sweden in %and, independently, by oseph Briestley in ?ngland in %C.

#amed from the 2reek ὀ345 oxys/ 6acid6, literally 6sharp6, referring to the sour taste of acids/ and 789:5 gen;s/ 6producer6, literally 6begetter6/, because at the time of naming, it was mistakenly thought that all acids rey mass, oxygen is the third most abundant element in the universe after hydrogen and helium/ and the most abundant in the ?arth(s crust.

Eree oxygen is too reactive to exist on ?arth without the photosynthetic action of living organisms, and began to accumulate in the atmosphere only after these organisms evolved about $F billion years ago.

)argest dinosaurs exist

Spread of plants O$ from oceans

Dolcanic activity, mass extinctions

Impact event, mass extinctions

Argon, Ar, is the third most common gas in the atmosphere. The name 6argon6 is derived from the 2reek word meaning 6la=y6 or 6the inactive one6, a reference to the fact that the element undergoes almost no chemical reactions. It is used mostly as an inert gas shield in welding and other high temperature activities. It is also used in fluorescent lighting and for bluegreen gas lasers. Argon was first isolated in %!'C by )ord Jayleigh

Annually, concentrations peak in Kay as the #orthern 0emisphere spring greenup begins and reach a minimum in October when the