Chemical bonding is the major part of chemistry which is an interaction between two or more atoms that holds them together by reducing the potential energy of their electrons. In other words Bonds are the like chemists “glue” – which hold atoms together in molecules or ions. Valence electrons are the outer shell electrons of an atom which take part in chemical bonding.
Atoms gain or lose electrons to attain a more stable noble gas – like electron configuration (octet rule). There are two ways in which atoms can share electrons to satisfy the octet rule:
Ionic Bonding – occurs when two or more ions combine to form an electrically-neutral compound
The positive cation “loses” an electron (or 2 or 3)
The negative anion “gains” the electron (or 2 or 3)
The anion steals the electrons from the cation.
Covalent Bonding – occurs when two or more atoms combine to form an electrically-neutral compound.
The electrons are shared between the two atoms.
Both atoms don’t have charge in the beginning and the compound remains with zero charge.
The chemical activity of an atom is determined by the number of electrons in its valence shell. With the help of concept of chemical bonding one can define the structure of a compound and is used in many industries for manufacturing products.
Chemical reactions mostly take place in solutions. Solution chemistry plays a very significant role in chemistry. All chemical substances are made up of either polar units (called ions) or non-polar units. The activity of these entities is more evident and pronounced in solution. The behaviour of these substances depends upon their nature and conditions of the medium in which they are added. It is therefore necessary to understand the principles that govern their behaviour in solution.
This type of equilibrium is observed in substances that undergo ionization easily, or in polar substances in which ionization can be induced. Ionic and polar substances are more easily soluble in polar solvents because of the ease of ionization taking place in the solvent medium. With the dissolution of ionic and polar substances in the solvent, these solutions become rich in mobile charge carriers (ions) and thus can conduct electricity. Substances, which are capable of conducting electricity are called as electrolytes while those substances which are non-conducting are called as non-electrolytes.
States of matter is of prime importance to physicists. Everyday elements and compounds form three states of matter, however there are many other states, less common but equally important.
The liquid-crystal state of certain compounds has the properties of solids as well as liquids, and is the basis of electronic displays. More states are obtained when the particles are lighter.
The electrons in metals and ceramics undergo a change due to which electricity is conducted without dissipation.
Study States of matter for Preparation of IIT JEE AIEE at askiitians, with several underlined topics and important examples. All provided to you by ex IITians. States of matter as explained above is important both from exam as well as research point of view for future reference.
This chapter besides being simple is very important too especially the section dealing with Raoultâ€™s Law , Colligative properties and Vanâ€™t Hoff Factor.Colligative properties are those properties of solutions that depend on the number of dissolved particles in solution, but not on the identities of the solutes. For example, the freezing point of salt water is lower than that of pure water, due to the presence of the salt dissolved in the water.
To a good approximation, it does not matter whether the salt dissolved in water is sodium chloride or potassium nitrate; if the molar amounts of solute are the same and the number of ions are the same, the freezing points will be the same. For example, AlCl3 and K3PO4 would exhibit essentially the same colligative properties, since each compound dissolves to produce four ions per formula unit. The four commonly studied colligative properties are freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure. Since these properties yield information on the number of solute particles in solution, one can use them to obtain the molecular weight of the solute.
Oxidation can be defined as the loss of electrons by an atom or ion, while Reduction can be called as the gain of electrons by an atom or ion. Neither reduction nor oxidation occurs alone. Both of them occur simultaneously. Since both these reactions must occur at the same time they are often termed as “redox reactions”.
The oxidation or reduction portion of a redox reaction, including the electrons gained or lost can be determined by means of a Half-Reaction:
Fe3+(aq.) + 3e– â†’ Fe(s)
Fe(s) â†’ Fe3+(aq.) + 3e–
The substance that causes the oxidation of a metal is called the oxidizing agent. Or in other words, the Oxidizing agent is the substance being reduced. The substance that causes the reduction of the metal is called the reducing agent. Or in other words reducing agent gets oxidized (undergoing oxidation).
Redox reactions are mainly of two types:
â€¢ Inter Molecular Redox Reactions
â€¢ Intra Molecular Redox Reactions
It is very important to master these concepts at early stage as this forms the basis of your preparation for IIT JEE, AIEEE, DCE, EAMCET and other engineering entrance examinations.
Surface chemistry is the study of chemical phenomena that occurs at the interface of two phases, usually between a gas and a solid or between a liquid and a solid. It can be roughly defined as the study of chemical reactions at interfaces. One of the important aspects of surface chemistry study is to determine whether a molecule attaches itself to a surface by chemisorption or by physisorption. Surface chemistry is of particular importance to the field of heterogeneous catalysis. It is the surface chemistry which deals with Colloidal states which finds a lot of uses.
From the IIT JEE point of view it is really easy to score marks in the questions based on this topic as the questions are direct and simple.
Electrochemistry encompasses chemical and physical processes that involve the transfer of charge. It deals with the interactions of electrical energy with chemical species. It is broadly divided into two categories, namely (i) production of chemical change by electrical energy (phenomenon of electrolysis) and (ii) conversation of chemical energy into electrical energy, i.e., generation of electricity by spontaneous redox reactions. In this section, we will discuss Faradayâ€™s Laws of Electrolysis, Applications of Electrolysis, Electrochemical cell, Daniell Cell, Electrode Potential, Emf of a Galvanic Cell, Solved examples on Electrochemistry etc.
Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction’s mechanism and transition states, as well as the construction of mathematical models that can describe the characteristics of a chemical reaction. In 1864, Peter Waage and Cato Guldberg pioneered the development of chemical kinetics by formulating the law of mass action, which states that the speed of a chemical reaction is proportional to the quantity of the reacting substances. Concept of order of reaction and how to determine order of reaction along with integrated rate laws are the most important topics of this chapter. Repeatedly questions appear in IITJEE and AIEEE from these topics.
What is Isomerism?
In the study of organic chemistry we come across many cases when two or more compounds are made of equal number of like atoms. A molecular formula does not tell the nature of organic compound; sometimes several organic compounds may have same molecular formula. These compounds possess the same molecular formula but differ from each other in physical or chemical properties, are called isomers and the phenomenon is termed isomerism (Greek, isos = equal; meros = parts).
Since isomers have the same molecular formula, the difference in their properties must be due to different modes of the combination or arrangement of atoms within the molecule. Broadly speaking,there are two types of isomerism:
1. Structural Isomerism 2. Stereo Isomerism
â€‹When the isomerism is simply due to difference in the arrangement of atoms within the molecule without any reference to space, the phenomenon is termed structural isomerism. In other words, while they have same molecular formulas they possess different structural formulas. This type of isomerism which arises from difference in the structure of molecules, includes:
1. Chain or Nuclear Isomerism; 2. Positional Isomerism 3. Functional Isomerism 4. Metamerism and 5. Tautomerism
When isomerism is caused by the different arrangements of atoms or groups in space, the phenomenon is called Stereoisomerism (Greek, Stereos = occupying space). The stereoisomers have the same structural formulas but differ in the spatial arrangement of atoms or groups in the molecule. In other words, stereoisomerism is exhibited by such compounds which have identical molecular structure but different configurations.Stereoisomerism is of two types:
1. Geometrical or cis-trans isomerism 2. Optical Isomerism.
Carbon atoms have a versatile nature to attach themselves to one another to an extent not possible for any other element. Carbon atoms can form long chains and rings containing thousand of atoms. The chains and rings can be branched and cross-linked. This versitile nature of carbon is the reason why there are millions of compounds of carbon present around us. Organic molecules are everywere around us.These are the part of not our body but also food & medicins. Organic chemistry is vey important for technology also as it is chemistry of ink, papaer, dyes, paint, galsoline, rubber and plastic. As it is mentioned above, there are millions of organic compounds around us, it becomes very important to classify them in groups in order to study them properly. Further as organic compounds play a very important role in our life, it is also important to identify and name them all. In this chapter we will study about the classification of organic compounds and their nomenclature and also about the techniques used for their purification.
The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. They are a subset of the halocarbons, similar to haloalkenes and haloaromatics. They are known under many chemical and commercial names. As flame retardants, fire extinguishants, refrigerants, propellants and solvents they have or had wide use. Some haloalkanes (those containing chlorine or bromine) have been shown to have negative effects on the environment such as ozone depletion. The most widely known family within this group is the chlorofluorocarbons (CFCs).
In chemistry, an alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. The general formula for a simple acyclic alcohol is CnH2n+1OH. In common terms, the wordalcohol refers to ethanol, the type of alcohol found in alcoholic beverages.
Ethanol is a colorless, volatile liquid with a mild odor which can be obtained by the fermentation of sugars. (Industrially, it is more commonly obtained by ethylene hydration-the reaction of ethylene with water in the presence of phosphoric acid.) Ethanol is the most widely used depressant in the world, and has been for thousands of years. This sense underlies the term alcoholism (addiction to alcohol).
Other alcohols are usually described with a clarifying adjective, as in isopropyl alcohol (propan-2-ol) or wood alcohol (methyl alcohol, or methanol). The suffix -ol appears in the “official” IUPAC chemical name of all alcohols.
There are three major subsets of alcohols: primary (1Â°), secondary (2Â°) andtertiary (3Â°), based upon the number of carbon atoms the C-OH group’s carbon is bonded to. Ethanol is a simple ‘primary’ alcohol. The simplest secondary alcohol is isopropyl alcohol (propan-2-ol), and a simple tertiary alcohol is tert-butyl alcohol (2-methylpropan-2-ol).
In The later part of 1950 resulted in classic advance in the knowledge of how living cells engage themselves with molecules such as carbohydrates additionally the metabolism of carbohydrates also became clarified. In Biochemistry Carbohydrates belong to basic category of chemical compounds. They are biological means of consuming energy or storing energy; other forms being via fat and protein. Complex carbohydrates are known as polysaccharides.
Amino acids and Peptides link in a head-to-tail style, i.e. the molecules are bounded by ionic interactions and H-bonds involving Î±-amino and Î±-carboxylate groups. Further, from several crystal structures it was confirmed that head to tail arrangement is unaffected by presence of water molecules. However, in the hydrated cases the case is different.
Askiitians provides free Study Material – Course Material for IIT JEE AIEEE preparation in Carbohydrates Amino Acids and Peptides. From the examination point of view Biomolecules and carbohydrates are very important in better understanding of many graduate courses specifically medical.
What are hydrocarbons?
The term â€˜hydrocarbonâ€™ is self â€“explanatory which refers to the compounds formed by combination of carbon and hydrogen only. Hydrocarbons have very important role in our daily life. The Vegetable oil which is part of our food and also the gasoline which we use to run our vehicles is hydrocarbons. Hydrocarbons are the source of energy. The oil, ghee & butter are the hydrocarbon which are part of our diet and provide our body with energy required to perform various physical and biological functions.
LPG, CNG, LNG , Petrol, Diesel and Kerosene oil are the hydrocarbons which are used as fuels for automobiles and domestic uses. LPG is the abbreviated form of liquified petroleum gas, LNG is the abbreviated form of liquified natural gas whereas CNG stands for compressed natural gas. Petrol, diesel and kerosene oil are obtained by the fractional distillation of petroleum found under the earthâ€™s crust while coal gas is obtained by the destructive distillation of coal.
Hydrocarbons are also used for manufacture of polymers like polythene, polypropene, polystyrene etc and also as solvents for paints. They are also used as the starting materials for manufacture of many dyes and drugs.
Classification of Hydrocarbons
â€‹Hydrocarbons are broadly divided into aliphatic hydrocarbons and aromatic hydrocarbons. Aromatic hydrocarbons or arenes are the cyclic hydrocarbons with alternating double and single bonds betweeen carbon atoms. Benzene is an example of aromatic hydrocarbon.
Aliphatic hydrocarbons can further be divided into saturated hydraocarbons or alkane and unsaturated hydrocarbons. Saturated hydrocarbons cotain only single bonds throughout the length of carbon chain.
Unsaturated hydrocarbons contain one or more multiple bonds i.e double or triple bond, between the carbon atoms anywhere throughout the carbon chain. Unsaturated hydrocarbons with double bonds between the carbon atoms are called alkenes while those with triple bonds are called alkynes.
There is another class of aliphatic hydrocarbons called alicyclic hydrocarbons. These hydrocarbons are present in the form of rings.
Hydrogen is the most abundant element in universe and third most abundant element on the surface of earth. It is the simplest element with only one electron in its orbit around the nucleus congaing only one proton. It exist as a diatomic molecule i.e. H2 in its elemental form. The global concern related to clean energy makes it so important to study hydrogen separately from the other elements. This concern can be overcome to a greater extent by the use of hydrogen as a source of energy.
Position of Hydrogen in Periodic Table:
Hydrogen is the first element of periodic table but its position in the periodic table has been a subject of discussion for the past few years due to its similarities with both halogens and alkali metals. A proper position could not be assigned to hydrogen either in the Mendeleevâ€™s periodic table or Modern periodic table because of the following reason: In some properties, it resembles alkali metals and in some properties it resembles halogens. So hydrogen can be placed both in group 1 and group 17 with alkali metals and halogen respectively.
Isotopes of Hydrogen:
Hydrogen has three isotopes: Protium 1H1, or H , Deuterium 2H1 or D & Tritium 3H1 or T. These all differ from each other in respect of number of neutrons present in the nucleus. Protium does not contain any neutron, Deutrium ( also known as heavy hydrogen) contains one neutron while the number of neutrons in the nucleus of tritium is 2. Tritium is radioactive and emits low energy Î²– particles.
|Name of Isotope||Symbol||Atomic Number||Mass Number||Relative Abundance|
|Protium||1H1 or H||1||1||99.99%|
|Deuterium||2H1 or D||1||2||0.015%|
Resemblance with alkali metals
- Electronic configuration:
Hydrogen contains one electron in the valence shell like alkali metals
- Electropositive Character Like alkali metal, hydrogen also loses its only electron to form hydrogen ion, i.e, H–
- Oxidation state :Like alkali metals, hydrogen exhibits an oxidation state of +1 in its compounds.
- Reducing agent : Alkali metals act as reducing agents because of their tendency to lose valence electron. Hydrogen is also a very good reducing agent as evident from the following reactions:
- Combination with electronegative elements : Just like alkali metals hydrogen combines with electronegative elements such as halogen, oxygen, sulphur, etc to form compounds with similar formulae
Difference from Alkali Metals
- Ionization enthalpy : Ionization enthalpy of hydrogen (1312 kJ mol-1) is very high in comparison with the ionization enthalpy of alkali metals.
- Existence of H– : It has been established that H–ion does not exist freely in a aqueous solution. This is because of the fact that has a very small size as compared to normal atomic and ionic size (which range from 50 to 220 pm). Thus it exists in aqueous solution in the form of hydrated proton with a formula,H9O4–. However, for the sake of simplicity hydrated proton is represented by hydronium ion,H3O+.
On the other hand, the alkali metal ions mostly exist as hexahydrated ions.
- Difference in halides
Hydrogen halides are different from the halides of alkali metals although they have similar molecular formulae. For example
(i) Pure HCl is a covalent compound while NaCl is an ionic compound.
(ii) HCl is a gaseous compound while NaCl is a solid at ordinary temperature.
Resemblance With Halogens
- Electronic configuration.
Just like halogens, hydrogen needs one electron to attain the configuration of nearest noble gas.
- Atomicity. Like halogens, hydrogen also exists in a diatomic state. The atomicity of hydrogen as well as halogens is two.
- Electrochemical nature.
During electrolysis of LiH, CaH2, etc, in molten state hydrogen is evolved at the anode indicating its electronegative nature. In this respect, hydrogen shows resemblance with halogens which are also liberated at the anode during electrolysis.
- Oxidation state.
Just like halogens, hydrogen also exhibit state of -1 in some of its compounds such as metal hydrides.
- Combination with alkali metals.
Just like halogen, hydrogen also combines with alkali metals to form salts with similar formulae.
6. Combination with non-metals: Just like halogens hydrogen also react with non-metals such as carbon, silicon, germanium, etc, to form covalent compounds.
- Ionization energy
Ionization energy of hydrogen is comparable to the ionization energies of halogens as shown below:
|Ionization energies (Kj mol-1)||1312||1681||1255||1121|
The outermost orbital of s block elements consists of one or two electrons. Next to the outer most penultimate shell has either 2 or 8 electrons. s-block elements show a fixed valency which depends on the number of electrons present in the outermost shell.
Except hydrogen , all s-block elements have low values of ionisation potential decreases in the case of alkali metals and alkaline earth metals as the atomic number increases. Ionisation potential increases on moving horizontally from IA to IIA. On account of low values of ionisation potentials , these elements are highly electropositve , i.e., easily lose valency electrons and form cations.
The elements of groups of p block elements exhibit a range of properties. Many of the trends observed in this group can be understood from considerations of their electron configurations and their respective positions in the periodic table. For example, the inert pair of valence-shell electrons retained in the Ti+ ion is also found in several other cations following a transition series.
The elements that lie in between S-block and P-block are the d-block elements. These elements are called transition elements as they show transitional properties between s and p-block elements. These elements contain partially filled d-orbitals and hence they are called as d-block elements.
The f-block of the periodic table of the elements consists of those elements whose atoms or ions have valence electrons in f-orbitals. Actual electronic configurations may be slightly different from what is predicted by the aufbau principle. The elements are also known as inner transition elements.
This section includes the important topics like screening effect, periodic table, hydration energy, magnetic and periodic properties etc.
Co-ordination compounds are the compounds in which the central metal atom is linked to ions or neutral molecules by co-ordinate bonds, e.g. [Cr(H2O)5Cl]2+.
Coordination Compounds includes topics like Ligands, IUPAC Nomenclature, Isomerism, Valence Bond Theory and Organometallic Compounds etc which are very important from the point of view that these are prerequisite to Inorganic chemistry Sections. It is very important to master these concepts at early stage as this forms the basis of your preparation for IIT JEE, AIEEE, DCE, EAMCET and other engineering entrance examinations.