Category: Chemistry Notes PPT

The reaction of Fenton is a reaction in which hydrogen peroxide is converted through a catalytic method into a hydroxyl free radical. The hydrogen peroxide reactant is normally formed by oxidative respiration from the mitochondria. It is important to note that during the Fenton reaction, the hydroxyl free radical is extremely toxic (due to its unstable and reactive nature). The reaction is named after Henry John Horstman Fenton, a British chemist.

Fenton’s Reagent

Fenton’s reagent is a term used to describe a solution containing the ferrous ion of hydrogen peroxide (the Fe2+ cation in which iron has an oxidation state of +2). The ferrous ion serves as a catalyst and facilitates pollutants and wastewater oxidation. It can be noted that the Fenton reagent is normally prepared by dissolving iron(II) sulfate (FeSO4) in hydrogen peroxide.

For the degradation of such organic compounds such as tetrachloroethylene and trichloroethylene, Fenton’s reagent may be used. It should also be remembered that Henry Fenton invented Fenton’s reagent as an analytical reagent in the 1890s.

Breakdown of Fenton’s Reaction

In the presence of hydrogen peroxide, which acts as an oxidizing agent, Fenton’s response starts with the oxidation of the ferrous ion (Fe2+ cation) to the ferric ion (Fe3+ cation). This results in the formation of a hydroxide ion as byproducts and a hydroxyl free radical. The chemical equation is given below for this reaction.

Fe2+ + H2O2 → Fe3+ + OH– + HO•

Now, in the next step of Fenton’s reaction, in the presence of another hydrogen peroxide molecule, the ferric ion is reduced back into the ferrous ion. This results in the formation of a free radical of hydroperoxyl and a proton as the byproducts. The ferrous ion catalyst is thus regenerated. The chemical equation is given below for this step of Fenton’s reaction.

Fe3+ + H2O2 → HOO• + Fe2+ + H+

Therefore, when hydrogen peroxide molecules undergo disproportionation in Fenton’s reaction, two separate oxygen free radicals are generated. It should be noted that ions and protons of hydroxide are also formed as byproducts that combine to form water. The chemical equation for the entire reaction can be written as follows:

2H2O2 → HOO• + HO• + H2O

The presence of ferric ions in the solution of hydrogen peroxide thus promotes the disproportionation of the H2O2 molecules, leading to the development of highly toxic free radical species such as the free radical hydroxyl. Generally, the free radicals that are produced during the reaction of Fenton participate in secondary reactions (since the hydroxyl free radical is a very powerful, non-selective oxidizing agent). They undergo rapid oxidization in a strongly exothermic reaction when organic compounds are exposed to Fenton’s reagent. Water and carbon dioxide are normally oxidized by toxins.

How Does the pH of the Environment Affect Fenton’s Reaction?

Ferric ions at neutral pH ranges are nearly 100 times less soluble than ferrous ions. The concentration of ferric ions in Fenton’s reaction is typically the limiting factor in the reaction rate. The pH of the environment therefore has a significant influence on the rate of reaction of Fenton.

Under acidic conditions, because of the increased solubility of ferric ions in acidic media, Fenton’s reaction proceeds at a very rapid rate. The reaction rate of Fenton’s response, however, slows down under alkaline conditions. The formation of ferric hydroxide may explain this (which precipitates out of the solution). As a result of the formation of ferric hydroxide, the decreased ferric ion concentration is the explanation behind the reduced reaction rate of the Fenton alkali reaction.

What is the Electro-Fenton Process? 

The electro-Fenton process requires the in situ production of hydrogen peroxide as a consequence of oxygen electrochemical reduction.

What are the Applications of Fenton’s Reagent?

In converting benzene into phenol, Fenton’s reagent can be used. In order to transform barbituric acid into alloxan, this reagent can also be used. In the hydroxylation of arenes, the Fenton reagent is also useful.

• The Haber-Weiss reaction, which is a called reaction producing hydroxyl radicals from superoxide and hydrogen peroxide, is based on the first stage of Fenton’s reaction (which requires the oxidation of ferrous ions with hydrogen peroxide).

• In organic synthesis reactions, Fenton’s reagent may also be used. For instance, with the aid of Fenton’s reagent, the hydroxylation of arenes through a free radical substitution mechanism can be achieved.

• By using Fenton’s reagent, benzene can be converted into phenol. 

• The Fenton reaction can also be used to oxidize alloxan into barbituric acid. 

• The coupling reactions of alkanes are another major application of Fenton’s reaction.

Fluorine is a halogen gas that belongs to the 17th group of the periodic table. The atomic number of the element is 9. The most characteristic feature about fluorine is that it is the most electronegative element in the periodic table. Its appearance can be described as a very toxic pale yellow diatomic gas at standard conditions. On the Pauling scale, the electronegativity of fluorine was measured to be 3.98 which surpassed every other element.

Electron Configuration And Chemical Properties of Fluorine

As we’ve seen earlier, fluorine is a gas belonging to the 17th group and fluorine atomic number is 9. Since fluorine is a halogen, it’s valency is one. It is an electron recipient and lacks 1 electron. Such elements accept electrons and hence are oxidizing agents. 

Remember: Electron acceptors are always oxidizing agents and electron donors are always reducing agents.

All the halogens are strong oxidizing agents out of which fluorine is the strongest due to its high electronegativity. The Electronic configuration of fluorine is 1s²2s²2p⁵. From the electronic configuration, we can clearly observe that the element lacks one electron. Hence, it is an electrophile and happily accepts an electron. 

Properties of Fluorine

Chemical Properties of Fluorine

• Fluorine is a highly electronegative element and is hence one of the strongest oxidizing agents. The electronegativity of fluorine as measured by the Pauling scale is 3.98. 

• The energy required to extract an electron is very high due to the strong force of attraction between the nucleus and the electrons owing to their small size. The first ionization energy of fluorine is 1680.6 KJ/Mol. That means, 1680.6 KJ energy is required to extract an electron from one mole of fluorine

• The standard potential of fluorine is 2.87 V. This is the highest among all other elements. 

• Fluorine has only one stable isotope, that is fluorine 19. 

Physical Properties of Fluorine

• The atomic mass of fluorine is approximately 19 and fluorine is the lightest among all other halogens. 

• Fluorine exists as a gas in nature and at a standard state. It has a pale yellow colour and is a light gas. 

• The boiling point of fluorine is -188° C and the melting point of fluorine is -219.6° C.

The Atomic Radius of Fluorine 

Fluorine is a tiny element with a really small atomic radius. Due to this, the nuclear force in a fluorine atom is extremely high. The atomic radius of fluorine is merely 147 pm, making it the smallest halogen atom.

What is The Atomic Mass of Fluorine? 

As we’ve seen earlier, fluorine is the lightest halogen gas and weighs only 19 amu, to be precise it is 18.99. However, by convention, we round it off and consider it as 19. 

To answer the question, “what group fluorine is in” and “what is the symbol of fluorine”,  Fluorine belongs to the halogen group that is the 17th group and the fluorine is represented as F2. 2 indicates the diatomic nature of fluorine gas.

Fun Facts About Fluorine

• Fluorine is the 13th most abundant element in the earth’s crust. 

• Fluorine is a highly reactive element and is never found in its original state. It is always found combined with some or the other elements. 

• Fluorine is capable of burning water with a bright flame.

• Apart from being found in the air, fluorine is also found in the earth’s crust. Traces of fluorine are found in coal and other elements.

• In the air, fluorine is present in almost negligible quantity. It’s about 50 parts per billion.

• Fluorine had no recognition in the industry until the 2nd world war. No one cared to industrially produce fluorine until then. Everyone just knew fluorine as an element which is capable of combining and making salts. However, in World War 2, people realized that uranium hexafluoride has nuclear properties and can be a source of energy. Since then, industrial production of fluorine rose exponentially.

Some Common Compounds Containing Fluorine

Fluorine is very small in size and hence it is difficult for fluorine to exist in ionic compounds. However, owing to its highly electrophilic nature, fluorine is highly reactive and hence forms several compounds. 

Some of The Popular Compounds Containing Fluorine Include

• Calcium Fluoride – CaF2

• Xenon Difluoride- XeF2

• Hydrogen Fluoride- HF 

• Uranium Hexafluoride (UF6)

• Sodium Monofluorophosphate (Na2PO3F)

• Sodium Fluoride (NaF)

• Stannous(II) fluoride (SnF2) 

• Dichlorodifluoromethane (CF2Cl2)

The particular temperature at which a liquid transforms into a solid is known as its Freezing Point. Like the melting point, the freezing point also rises when there is an increase in pressure.

When we talk about mixtures and specific organic compounds, their freezing point is lower than their melting point. When these mixtures begin freezing, the solid they form in the start has a different composition than that of the liquid.

This formation substantially changes the composition of the remaining liquids, this usually happens in a manner that lowers the freezing point slowly.

We can apply this same treatment in successive melting, purifying mixtures, and freezing.

Let us study the different types of freezing points, the factors affecting them, the supercooled liquid, and other concepts.

Freezing Point – Basics

As we discussed that freezing is the process where a substance changes its state from liquid to solid, we understand that in this process a substance is transforming from one state of matter into another.

We will call a point a freezing point if its solid and liquid states exist at the same time in the given equilibrium.

 

Freezing Point Defection

The freezing point is the temperature at which a liquid changes into solid, at normal atmospheric pressure. A more precise definition of a freezing point is the temperature at which liquid and solid phases coexist in the equilibrium. 

How Does Freezing Occur? – The Process

As the liquid freezes, it turns from a liquid state into a solid-state. This phenomenon occurs when a substance’s molecules are loosely bound. The intermolecular forces of attraction between the molecules are less than that of the solids.

In liquids, water molecules are always moving. They continuously bump into each other and are always in motion. This is the thermal energy between these molecules and this energy cools down when it freezes, as a result, these molecules come closer and turn the liquid-solid.

When a liquid like water freezes, its molecules settle down in one place, the forces attracted to one another hold these molecules together and solid crystals begin to form.

During this freezing process, the temperature of the substance remains the same. The particles in this liquid substance turn into crystalline solids, as the particles lose their energy when they are turning into solids, this energy gets released.

Fun Fact

A liquid’s freezing point is the same as its melting point in the solid-state. For example, water’s freezing point is 0° Celsius (32° Fahrenheit), but the melting point of water in its solid state is also 0° Celsius.

Factors Affecting the Freezing Point

Types of molecules: If the intermolecular forces between the molecules of a liquid are strong, its freezing point also becomes high.

In contrast, if the intermolecular forces of attraction between the molecules are weak, then its freezing point becomes low.

By observing these two facts we can say that the intermolecular forces of attraction are directly proportional to its freezing point.

Types of Changes in a Freezing Point

We observe that there are two kinds of changes, chemical and physical. These changes can affect a substance’s freezing point. We can sometimes also change the freezing point and melting point of a certain substance by mixing another soluble substance with it.

You can also obtain a lower freezing point by altering the pressure.

Supercooled Liquid

What if a liquid is cooled to an extreme but it is still a liquid substance?

This process is called supercooling a liquid, where we chill the liquid even beyond its freezing point and melting point without turning its state to solid.

Now in theory we know this is not possible, as the freezing point and melting point of a substance has to be the same. It applies to most substances.

However, there are few substances that have a slight difference between their melting and freezing points. These kinds of substances can get cooled beyond their freezing point and still stay in their liquid state. These are substances that are known as Supercooled Liquids.  

The most well-known example of a supercooled liquid is the clouds at high altitudes that are nothing but a collection of supercooled water droplets that are below their freezing point.

With over 13 natural isotopes and known for its wide range of applications today, Gadolinium is the 66th element in the Periodic Table. Denoted as Gd, this element is classified under the section of lanthanides. Malleability, solubility, ductility, and high thermal stability are all the notable features of this chemical element. The important, booming fields of technology and medical sciences, prefer Gadolinium over others considering its chemical and physical properties. Let us hence learn about the important basics of Gadolinium’s properties, applications and other interesting facts on the go.

A Quick Note of What Gadolinium is

The discovery of Gadolinium (The element’s symbol is Gd) dates back to 1880. The Swiss chemist ‘Jean Charles Galissard de Marignac’ found Gadolinium by using the method of spectroscopic line detection over the compound Gadolinia. Following which, the 1st isolation was a success in 1886, by the French chemist ‘Paul Émile Lecoq de Boisbaudran’ by separating this element Gadolinium from “Gadolinia ”. 

In the absence of an oxidized state, Gadolinium is a silvery-white lanthanide metal, present in the 66th position of the f-block and the 6th row of the Periodic Table. The compound’s atomic number is 64. Nuclear reactors, radiography, electronic device production, metallurgy and many other applications can be listed for using Gadolinium in the areas of technology, arts and science, engineering, medicine, etc.

The Notable Physical Properties of Gadolinium

• Solid structure at  20°C STP (Standard Conditions for Temperature and Pressure).

• Position of Gadolinium in the Periodic Table is 66, f-Block, 6th row, put under the category of lanthanides. 

• Toxicity is said to be lower but triggers issues such as skin and eye irritation for human beings. No prominent effect over animals and plants due to Gadolinium. 

• Soft and silvery-white bright metal.

• The element is named with its primary mineral, Gadolinite.

• Gadolinium is both ductile and malleable. 

• [GAD-ə-LIN-ee-əm] is the pronunciation for Gadolinium. 

• The element is found in the earth’s crust at the range of 5.2 parts per million.

• One of the rarely observed metals on the earth.

• HCP (Hexagonal Close Packing) is the crystal structure. 

• Has good resistance to high-temperature conditions. 

• Has 13 naturally-derived isotopes and 27-synthetic isotopes. 

• Paramagnetic at room temperature and turns into a ferromagnetic substance at colder conditions (estimated to be above 20°C). 

• Gadolinium is a form of Primordial isotope. 

• When added together with sulfur, boron, selenium, nitrogen, carbon, arsenic, phosphorus, and silicon, the element Gadolinium will create binary compounds as a result of its chemical reaction. 

• Highest thermal stability is noted with the isotope 157 Gd.

Points Covering the Chemical Properties of Gadolinium

• Molecular Weight of Gadolinium is 157.25 g/mol-1.

• The atomic number is 64.

• The count of electrons per each shell is 2, 8, 18, 25, 9, and 2.

• Boiling point is 3273°C at 5923°F and 3546 K

• 7.90 is the Density (g / cm−3).

• [Xe] 4f7 5d1 6s2 is the electronic configuration of Gadolinium. 

• Trivalent bond formation during its compound state.

• Both the exact and monoisotopic mass value is 157.92411 g/mol.

• The presence of 1 Heavy Atom counted. 

• Estimated Molar Heat Capacity is 37.03 J/(mol·K).

• Highly reactive with other dilute acid forms.

• There is 1 Covalently-Bonded Unit.

• 17°C is the estimated value for the Curie Point. 

• 1313°C is the melting point of Gadolinium at 2395°F, 1586 K.

• Gadolinium is a Canonicalized element. 

• Unreactive with oxygen but in the presence of moist air, the element will tarnish and create a layer of white oxide, which is gadolinium(III) oxide (Gd2O3), for restricting further oxidation. 

Occurrence and Existence of Gadolinium and its Isotopes

154Gd, 155Gd, 156Gd, 157Gd, 158Gd, and 160Gd are the 6 major isotopes of Gadolinium. There are about 29 different radioactive isotopes for Gd, out of which, 152Gd is said to be the naturally-occurring isotope of Gd that possesses high stability. Note that the primary mode of decaying in Gadolinium is beta decay at conditions of higher atomic mass and the resulting product is an isotope of terbium. 

Even though the exact measure of producing Gadolinium varies annually, it is anyhow estimated to be around 400 tonnes per year. The metal is not present in the natural environment owing to its high reactivity. 

The lanthanide Gadolinium is noted to be found in specific mineral oxides such as bastnäsite and monazite. Even the mineral Gadolinite has only a sizable quantity of Gadolinium with it. ‘Lepersonnite-(Gd)’ is one of the key minerals known to be closely associated with Gadolinium and is extremely rare for existence. 

India, Sri Lanka, the United States of America, China, and Brazil are some of the notable countries, where 1 million is the estimated exceed of reserved value for Gadolinium. 

Real-Life Uses of Gadolinium with Examples

• Video recorders and other electronic devices are produced by making use of the alloys of Gadolinium.

• Gadolinium is used as a Dopant for producing fuel cells, as in the case of cerium oxide, which is one of the optimal and cost-effective methods. 

• In the case of a  CANDU reactor type, the isotope 157Gd is useful to impact in conditions of emergency shutting-down of nuclear programmes. Moreover, the same element is preferred as a burnable poison for nuclear marine propulsion.  

• To imitate diamond stones and jewellery, workers tend to use the Gadolinium Gallium Garnet (GGG, Gd3Ga5O12). 

• Colour Television Gadgets prefer Gadolinium in the form of Phosphorus and even to manufacture microwave-related appliances. Similarly, this change is noted in the case of x-ray machines, where Gadolinium acts as suspension for a polymer matrix in the region of detection. 

• Since Gadolinium has good resistance to high temperatures, the lanthanide is used in the making of other high-temperature gadgets. 

• Targeting the tumour cells during a neutron therapy is possible from using the isotope 157Gd. This applies even to nuclear reactors and neutron radiography techniques. 

• Magnetic Resonance Imaging (MRI) makes use of Gadolinium Contrast, owing to its paramagnetic ions where it enhances the nuclear relaxation rates.

Conclusion

Gadolinium is a silver-white coloured lanthanide metal, with atomic number 64 and present in the f-block’s 66th position in the Periodic Table. The element was discovered by a Swiss Chemist in 1880 and was isolated by a French Chemist in 1886. Gadolinium denoted as Gd has multiple radioactive isotopes and a vast majority of them are not found in the natural atmosphere due to its high reactivity. This compound is a solid structure with HCP formation at STP and has high resistive power to extremely heated conditions. Domains such as electronic production, chemical oxidation, diamond imitation, nuclear power plants, fuel cell generation, are some of the common instances where Gadolinium is preferred at different stages of production and manufacturing.

The Glauber’s salt is the decahydrate sodium sulphate form. It can also be called the mirabilite. The chemical formula for the Glauber’s salt is denoted by Na2SO4.10H2O. This salt is the vitreous mineral with the white or colourless appearance. This forms the evaporite from the brines comprising of the sodium sulphate. You should also note that the compound is known to form naturally along the saline springs and saline playa lakes. The name of the Glauber’s salt was given after the German-Dutch chemist and the alchemist – Johann Rudolf Glauber.

The Structure of the Glauber’s Salt

The decahydrate crystals contain the [Na(OH2)6]+ ions having octahedral molecular geometry. The octahedra shares the edges. 8 out of these 10 water molecules are further bound to the sodium, and the remaining two are hydrogen bonds, interstitial and they are bonded to the sulphate. The resulting cations are linked to sulphate anions via hydrogen bonds. The crystalline sodium sulphate decahydrate is uncommon amongst hydrated salts for having the moderate residual entropy of 6.32 J⋅K−1⋅mol−1. This indicates the ability of distributing water rapidly in comparison to most other hydrates.

The Properties of Glauber’s Salt

Physical Properties: The Glauber’s salt or the sodium sulphate the unusual soluble characteristics in the water. The solubility for this specific compound in the water goes up ten times ranging between 0 degrees celsius to 32.384 degrees celsius, and at that point it reaches 49.7g/100 ml as the maximum level. At this point, the curve of solubility changes into slope and solubility becomes considerably independent of the temperature. 

Chemical Properties: Typically, the sodium sulphate is the electrostatically bonded ionic sulphate. The existence of the free sulphate ions in the solution is represented by easy formation of insoluble sulphates when the solutions are treated with Pb2+ Ba2+ salts and the chemical equation is as follows: Na2SO4 + BaCl2 → NaCl + BaSO4. The Glauber’s salt tends to be unreactive towards most of the oxidising or reducing agents. It gets converted to sodium sulphide at higher temperatures with the help of carbothermal reduction. 

The Uses of Glauber’s Salt

Glauber’s salt is widely used as the laxative in numerous medications. This compound is also effective in the removal of excessive drugs, such as paracetamol, from the body when it is used in overdose. This compound is also useful for storing low-grade solar heat when it is transforming from the solid phase to the liquid phase. The chemical industry also uses Glauber’s salt for producing several important chemicals from a commercial point of view.

Chemical Properties

Typically, sodium sulphate is an electrostatically bonded ionic sulphate. The free sulphate ions’ existence in the solution is represented by the easy formation of the insoluble sulphates when these solutions are treated either with Pb2 + Ba2 + salts, where the chemical equation is listed below.

Na2SO4 + BaCl2 → 2 NaCl + BaSO4

Glauber’s salt is unreactive toward most reducing or oxidising agents. It is converted to the sodium sulphide at higher temperatures using the carbothermal reduction (heating with charcoal, and more, at high temperature) as represented with the chemical equation below.

Na2SO4 + 2C → Na2S + 2CO2

This chemical reaction was employed in the process of Leblanc, which is a defunct industrial route to the sodium carbonate.

Glauber’s salt reacts with the sulfuric acid to produce acid salt sodium bisulfate, where the chemical equation is represented below.

Na2SO4 + H2SO4 ⇌ 2 NaHSO4

Glauber’s salt shows a moderate tendency to form double salts. The only alums that are produced with common trivalent metals are NaCr(SO4)2 and NaAl(SO4)2 (unstable above 39℃), in contrast to ammonium sulphate and potassium sulphate, which form various stable alums. Double salts with a few other alkali metal sulphates are known, including the Na2SO4·3K2SO4 that occurs naturally similar to mineral aphthitalite. The formation of glaserite via sodium sulphate reaction with potassium chloride has been used as a method for the production of potassium sulphate, which is a fertiliser. Another double salt is NaF·Na2SO4.

Production of Glauber’s Salt

The world production of Glauber’s salt or sodium sulphate, almost exclusively in the decahydrate, amounts to nearly 5.5 to 6 million tonnes (Mt/a) annually. In 1985, the production was 4.5 Mt/a, which is half from natural sources and a half from chemical production. Whereas, after 2000, at a stable level until 2006, the natural production had tremendously increased to 4 Mt/a, and at the same time chemical production has decreased to 1.5 to 2 Mt/a, with 5.5 to 6 Mt/a as a total. For all the applications, chemically produced and naturally produced sodium sulphate are practically interchangeable.

In this article, we have discussed greenhouse gases’ meaning. This article will help the students in making a short note on greenhouse gases. This Greenhouse effect article will help the students in clearing the concepts of greenhouse gases and global warming.

Greenhouse Gases Definition– Greenhouse gases definition explains the meaning of greenhouse gas. These are the gases that absorb and emit infrared radiation in the wavelength range emitted by the earth. 

Let’s discuss which gas is called greenhouse gas? The examples of greenhouse gases in the earth’s atmosphere are: 

Examples of greenhouse gases such as carbon dioxide (CO2) and water vapour (H2O) are natural greenhouse gases. Examples of greenhouse gas such as methane are anthropogenic emission greenhouse gases. 

Contribution of Greenhouse Gases

89 % is contributed by the water vapour, 7 % is contributed by carbon dioxide, and the remaining percent is contributed by the other mentioned gases in the table.

What are Greenhouse Gas Emissions?

Greenhouse gas emissions are the emission of gases from various sources that cause global warming. The major emission source of greenhouse gases is an energy source and the least is contributed by the solvents.

Percentage contribution to Global Warming 

Before discussing this let’s discuss what is meant by greenhouse gases? Greenhouse gases are harmful environmental gases that are responsible for causing global warming.

Contribution 

Carbon dioxide (CO2) > Methane (CH4) > Chlorofluorocarbons (CFCS) > Nitrous oxide (N2O)

Carbon dioxide contribution = 60%

Methane contribution = 20%

Chlorofluorocarbons contribution = 14%

Nitrous oxide contribution = 6%

Water vapour is not listed due to the amount being variable in nature and not anthropogenic.  

Why is the Study of Greenhouse Gases necessary?

The answer to this question is similar to the question: what is the meaning of greenhouse gases? The greenhouse gases like methane, nitrous oxide, chloro fluoro carbons increases day by day due to the anthropogenic activities which trap the radiation of wavelength (7 to 13 micrometres) come under the atmospheric window and re-radiated back to the atmosphere and increase the temperature of the earth.

1. Carbon Dioxide

Absorbs radiation between 4 to 5 micrometre and 14-19 micrometre.

Concentration in pre-industrial time was 280 parts per million and in present-day its concentration is around 400 parts per million.

Residence time for carbon dioxide is 5 years to 200 years.

2. Methane 

Methane absorbs radiation between 3 to 5 micrometre and 7 to 8.5 micrometre.

Concentration in pre-industrial time was 750 parts per billion and in present-day it is around 1800 parts per billion.

3. Nitrous Oxide

Nitrous oxide absorbs radiation between 3 to 5 micrometre and 7.5 to 9 micrometre.

Concentration in pre-industrial time was 7270 parts per billion and in present-day it is around 330 parts per billion.

4. Tropospheric Ozone

Ozone absorbs edition between 9-10.6 micrometre 

Its concentration varies from place to place.

5. Halocarbons

Halocarbons absorb radiation around 9 micrometre in the frequency of the atmospheric window so that these are potent greenhouse gases and also play a role in depleting stratospheric ozone.

It can be divided into five categories:

• Chlorofluorocarbons (CFCs)

• Hydrochlorofluorocarbon (HCFCs)

• Hydro Fluoro Carbon (HFCs)

• Perfluorocarbon (FCs)

• Halones

The ozone-depleting potential of halocarbons is

Global Warming Potential (GWP)

Global warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It allows a comparison to be made between the global warming impact over a specified particular GHGs and simultaneous emission of an equal mass of carbon dioxide (CO₂). 

Order of magnitude of Global Warming Potential

Sulphur hexafluoride (SF6) > Halocarbons > nitrous oxide (N2O) > methane (CH4)> carbon dioxide (CO2).

Did You Know?

• Water provides a major contribution to the total greenhouse gases. Still, its contribution is not countable in causing global warming due to its variable concentration in the atmosphere.

•  The area of the electromagnetic spectrum where the atmosphere is transparent to specific wavelengths between 7 to 13.5 micrometers is called an atmospheric window.