Nitrogen : Lightest pnictogen
Nitrogen is a colorless, odorless, and tasteless gas composed of N2 molecules. Its melting point is −210°C, and boiling point is −196°C.
Occurrence and abundance
Though dinitrogen comprises 78% of the earth’s atmosphere, it is not a very abundant element in the earth’s crust.
Nitrates are all very soluble in water so they are not widespread in the earth’s crust, though deposits are found in a few desert regions.
The largest is a 450–mile–long belt along the coast of Northern Chile, where NaNO3 (chile saltpeter) is found together
with small amounts of KNO3, CaSO4 and NaIO3 under a thin layer of sand or soil.
This provided the main source of nitrates prior to World war I, when synthetic processes were developed for the manufacture of nitrates
from atmosphere dinitrogen. A major deposit of saltpeter KNO3 occurs in India.
Nitrogen was discovered in 1772 by the Scottish botanist Daniel Rutherford. He found that when a mouse was enclosed in a sealed jar, the animal quickly consumed the life–sustaining component of air (oxygen) and died. When the “fixed air” (CO2) in the container was removed, a “noxious air” remained that would not sustain combustion or life. That gas is known to us as nitrogen.