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Oxygen Cycle

It involves the inter- change of oxygen between the elemental form of gaseous O2, contained in a huge reservoir in the atmosphere, and chemically bound O in CO2, H2O, minerals, and organic matter. It is strongly tied with other elemental cycles, particularly the carbon cycle. Elemental oxygen becomes chemically bound by various energy-yielding processes, particularly combustion and metabolic processes in organisms. It is released in photosynthesis. This element readily combines with and oxidizes other species such as carbon in the process of aerobic respiration, or carbon and hydrogen in the combustion of fossil fuels such as methane: CH4 +  2O2    →   CO2    +  2H2O Elemental oxygen also oxidizes inorganic substances such as iron(II) in minerals: 4FeO4   +   O2   →    2Fe3O3 A particularly important aspect of the oxygen cycle is stratospheric ozone O3. A relatively small concentration of ozone in the stratosphere, more than 10 km high in the atmosphere, filters out ultraviolet radiati
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Nitrogen Cycle

 Nitrogen occurs prominently in all the spheres of the environment. The atmosphere is 78% elemental nitrogen, N2, by volume and comprises an inexhaustible reservoir of this essential element. Nitrogen, although constituting much less of biomass than carbon or oxygenoxygen, is an essential constituent of proteins. The N2 molecule is very stable so that breaking it down into atoms that can be incorporated with inorganic and organic chemical forms of nitrogen is the limit- ing step in the nitrogen cycle. This does occur by highly energetic processes in lightning discharges that produce nitrogen oxides. Elemental nitrogen is also incorporated into chemically bound forms. or fixed by biochemical processes mediated by microorganisms. The biological nitrogen is mineral- ized to the inorganic form during the decay of biomass. Large quantities of nitrogen are fixed synthetically under high-temperature and high-pressure conditions according to the following over- all reaction:              N2+3H
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Carbon Cycle

CARBON CYCLE: Carbon circulates through the carbon cycle. It shows that carbon may be pres- ent as gaseous atmospheric CO2 constituting a relatively small but highly significant portion of global carbon. Some of the carbon is dissolved in surface water and groundwater as HCO-3 or molecular CO2 (aq). A very large amount of carbon is present in minerals, particularly magnesium and calcium carbonates such as CaCO3. Photosynthesis fixes inorganic C as biological carbon. represented as (CH2O), which is a constituent of all life molecules. Another fraction of carbon is fixed as petroleum and natural gas, with a much larger amount as hydrocarbonaceous kerogen (the organic matter in oil shale), coal, and lignite. Manufacturing processes are used to convert hydro- carbons to xenobiotic compounds with functional groups containing halogens, oxygen, nitrogen, phosphorus, or sulfur. Although a very small amount of total environmental carbon, these com- pounds are particularly significant because of
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Cycles of Matter

 Very much connected with environmental chemistry, cycles of matter, often based on elemental cycles, are of utmost importance in the environment. Global geochemical cycles can be regarded from the viewpoint of various reservoirs, such as oceans, sediments, and the atmosphere, connected by conduits through which matter moves continuously among the hydrosphere, atmosphere, geo- sphere, biosphere, and, increasingly, the anthrosphere. The movement of a specific kind of matter between two particular reservoirs may be reversible or irreversible. The fluxes of movement for particular kinds of matter vary greatly as do the contents of such matter in a specified reservoir. Most cycles of matter have a strong biotic component, especially through the biochemical processesof plants and microorganisms. The cycles in which organisms participate are called biogeochemical cycles, which describe the circulation of matter, particularly plant and animal nutrients, through ecosystems. Most biogeochemica
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Environmental Chemistry

 Hello readers!  I hope you all doing well. Today we will discuss something about environmental chemistry.  The environment is defined as consisting of five spheres: the hydrosphere, the atmo- sphere, the geosphere, the biosphere, and the anthrosphere; that is, water, air, the Earth, life, and those parts of the environment consisting of human constructs and activities. The chemistry of the environment, environmental chemistry, may be defined as the study of the sources, reactions, trans- port, effects, and fates of chemical species in the hydrosphere, the atmosphere, the geosphere, and the anthrosphere and the effects of human activities thereon. The pollutant sulfur dioxide is generated during the combustion of sulfur in coal, transported to the atmosphere with flue gas, and oxidized by chemical and photochemical processes to sulfuric acid. Sulfuric acid, in turn, falls as acidic precipitation, where it may have detrimental effects such as toxic effects on trees and other plants. Eve
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Structure of Atom (Part 6)

Bohr's Atomic Theory: Keeping in view the defects in Rutherford's Atomic Model, Neil Bohr presented another model of atom in 1913.The Quantum Theory of Max Planck was used as foundation for this model. According to Bohr's model, revolving electron in an atom does not absorb or emit energy continuously. The energy of a revolving electron is 'quantized' as it revolves only in orbits of fixed energy, called 'energy levels' by him.  The Bohr's atomic model was based upon the following postulates: i. The hydrogen atom consists of a tiny nucleus and electrons are revolving in one of circular orbits of radius ‘r’ around the nucleus. ii. Each orbit has a fixed energy that is quantized.  iii. As long as electron remains in a particular orbit, it does not radiate or absorb energy. The energy is emitted or absorbed only when an electron jumps from one orbit to another. iv. When an electron jumps from lower orbit to higher orbit, it absorbs energy and when it jumps
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Structure of Atom(Part 5)

 Rutherford's Atomic Model: Rutherford performed 'Gold Foil' experiment to understand how negative and positive charges could coexist in an atom. He bombarded alpha particles on a 0.00004  cm thick gold foil. Alpha particles are emitted by radioactive elements like radium and polonium. These are actually helium nuclei (He2+). They can penetrate through matter to some extent. He observed the effects of α-particles on a photographic plate or a screen coated with zinc sulphide. He proved that the 'plum-pudding' model of the atom was not correct.  Observations made by Rutherford were as follows: i.Almost all the particles passed through the foil un-deflected. ii.Out of 20000 particles, only a few were deflected at fairly large angles and very few bounced back on hitting the gold foil. Results of the experiment: Keeping in view the experiment, Rutherford proposed planetary model for an atom and concluded following results: i.Since most of the particles passed through th
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