Some Information On Nitrogen
According to the Greek words "nitron" and "genes", which together mean "saltpetre forming". Nitrogen was discovered by the Scottish physician Daniel Rutherford in 1772. Nitrogen is a chemical element having atomic number 7 in the periodic table. It's a colorless, odorless and tasteless gas. It's the fifth most abundant element in the universe and it appears in great plenteousness in earth's atmosphere constituting 78.09% by volume of it, which contains around 4,000 trillion tons of the gas..It's a nonmetallic gas.It has atomic weight of 14.0067,melting Point 63.15 K (-210.00°C or -346.00°F), boiling Point 77.36 K (-195.79°C or -320.44°F), density 0.0012506 grams per cubic centimeter.
It also appears in a number of other compounds and forms, and is a important component of life on earth for many organisms and species. It's extremely important for plants, animals and humans as they can't live without it. Nitrogen is a component of many organic molecules which is essential for for growth and reproduction in plants, animals and humans. It forms an essential part of amino acids that make up proteins, in nucleic acids and DNA that comprise the hereditary material and life’s blueprint for all cells, and in many other organic and inorganic compounds.
Different Forms of Nitrogen
Under standard temperature and pressure nitrogen is a gas, composed of a diatomic molecule of formula N2.It has 2 stable isotopes. The ionization energy of nitrogen is 14.534 eV. It has oxidation states like +5, +4, +3, +2, +1, -1, -2, -3. It forms triple bond unlike oxygen. This makes it one of the strongest chemical bonds(Energy of dissociation = 944.7 kJ mol-1), which is primarily responsible for the inertness of N2. Once the strong triple bond is broken, however,the nitrogen atoms are very reactive indeed and nitrogen forms many compounds with different types of bond. For example, nitrogen can form nitride ions, N-3, normal (sigma bonds), single bonds as in ammonia (NH3), or double bonds as in the diazo-dyes (R-N=N-R) or triple bonds as in N2 or cyanide), or the ammonium ion, NH4+. Nitrogen forms oxides in which nitrogen exhibits each of its positive oxidation numbers from +1 to +5. It forms a special chemical compound with oxygen having chemical formula N2O or nitrous oxide which is called laughing gas.
Nitrogen Cycle
For plants and animals to utilise nitrogen, two things should happen:
- The nitrogen gas in the atmosphere must find its way into the soil.
- The inert N2 must be broken down into more reactive compounds that are easier to metabolise.
One mechanism for this occurs during thunderstorms, when lightning flashes provide the high energies necessary to split the N2 bond and allow it to react with oxygen to form nitrogen oxides, such as NO and NO2. These can then dissolve in the water vapour in clouds to form nitric acid and nitrous acid (HNO3 and HNO2, respectively), which then rain down onto the waiting plants, which absorb it through their root systems.Due to the inertness of nitrogen Plants cannot directly use this form of it, so it must be converted into other forms before it can be used by plants. Some bacteria can convert the inert nitrogen into usable nitrogen compounds which is called fixation.
The main processes in Nitrogen Cycle are
- Nitrification
- Denitrification
- Nitrogen Fixation
In nitrification process the conversion of NH4- to NO3 happens via NO2. This is carried out by some aerobic and chemoautotrophic bacteria.The biochemical reaction is:
NH2OH + HNO2 => NO2.NH.OH + 2[H]
hydroxylamine + nitrous acid -> nitrohydroxylamine
Next stage is a direct oxidation step
NO2.NH.OH + 1/2 O2 => 2HNO2
nitrohydroxylamine, nitrous acid.
In denitrification conversion of NO3 to N2 gas. Many different kinds of facultative anaerobic bacteria can carry out this process; the most common are Pseudomonas spp., Achromobacter spp., Paracoccus spp., Moraxella spp., Bacillus spp., Alcaligenes spp., and Gluconobacter spp.are called nitrate reductase.
Overall reaction
2HNO3 => 2HNO2 => HON=NOH(hyponitrite)=> N2
In nitrogen fixation a specialized group of bacteria, and industrial fertilizer manufacture, can "fix" (decompose) this largely inert compound into biologically useful nitrogen compounds. During the processes of decomposition, the nitrogen in proteins is transformed eventually to ammonia, (NH3) or ammonium (NH4+). These processes are called ammonification. The nitrogen which has been fixed now available for plants to absorb. The nitrogen fixing bacteria form nitrates from of the atmospheric nitrogen which can be consumed and dissolved in soil water by the roots of plants. Then, the nitrates are incorporated by the plants to form proteins, which can then be spread through the food chain.
The complete nitrogen cycle is as follows.
Nitrogen gas=>Nitrogen fixation=>Organic nitrogen=>Ammonification=>Ammonium=>Nitrification=>Nitrate,Nitrite=>Denitrification=>Nitrogen gas.
Animals then eat the plants and convert the nitrogen into proteins. When the animals die, bacteria break down the proteins releasing N2 back into the atmosphere to begin the cycle again.
Industrial Use of Nitrogen
The largest use of nitrogen is for the production of ammonia (NH3). Large amounts of nitrogen are combined with hydrogen to produce ammonia in a method known as the Haber process. Large amounts of ammonia are then used to create fertilizers, explosives and, through a process known as the Ostwald process, nitric acid (HNO3).
It's obtained by cooling air below the boiling point of N2 and separating it from the rest of the components in air. N2 gas is used as an inert atmosphere in the manufacture of semiconductors and glass. Liquid nitrogen is used as a coolant.
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