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WHAT IS CHEMICAL ENGINEERING?

This 1990 Annual Meeting of the AIChE is the largest ever meeting of chemical
engineers -- a field now so diverse that it divides into 21 parallel lines of interest,
spread over five days.

There are 314 sessions, during which more than 2000 chemical engineers will
present their latest contributions -- each convinced that they are adding to the core of chemical engineering knowledge -- or perhaps, since the Amundson Report, they
would prefer to think of themselves as working at the frontiers, pioneers in expanding the horizons of chemical engineering.

But what is this "chemical engineering" that generates so much enthusiasm ?
What is it that all these people feel they share as a common profession ?
I don't know if the AIChE has a formal definition, but the I Chem E in its early
days gave great thought to the problem, and produced the following definition :

"Chemical engineering is the branch of engineering concerned with processes in which materials undergo a required change in composition, energy content or physical state, with the means of processing, with the resulting products and with
their application to useful ends.

This nails the flag of chemical engineering to the mast of engineering,defined in
turn by the Engineering Council, London, as follows :
"An engineer is one who acquires and uses scientific, technical
and other pertinent knowledge and skills to create, operate and
maintain efficient systems, structures, machines, plant, processes
and devices of practical and economic value."

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Force of attraction which hold two atoms together is called chemical bond.                                         
Example: H + H ------> H2 + heat                                                                                                     

why atoms form bond?                                                                                                                     
There are two main reasons due to which atom form bond.                                                       

Reason No 1: When two atoms combine to form a bond then heat is released, so the form substance become more stable at low energy.Thus atom form bond to acquire more stability at low energy.                                                                                                                                                             
Reason No 2: Atom form bonf=d to acquire the noble gas electrinic configuration in the valance shell.In noble gasses hilium has first valance shell and it has two noble gasses have eight electrons (octet) in valance shell.Generally noble gasses are stable and do not form bond like other elements.Thus ataom of other element form bond to acquire noble gas electronic configuration two electrons for the first valance shell and eight electrons for the other valance shells.                             

Types of Chemical Bond:

Different types of chemical bond are given below.
                                                                       
1)Ionic or Equivalent Bond
Bond form by transfer of one or more electron from the valance shell of one atom to the valance shell of other atom is called ionic bond.
or
Electrostatic force of attraction between cations and anions is called ionic bond.                               

Explanation:

Ionic bond is formed between metal andnon metal atoms if difference of electronagativity between them is more than 1.7.Metal atoms has low ionization potential and low electronagativity so they give electrons easily.Non metal atom has hugh electronagativity and high electro affinity so they gain electron easily.Thus in ionic bond metal give electron to acquire noble gas electronic configuration and change into cations and non metal  atom gain electron to acquire noble gas eletronic configuration and change into anions.Then the force of attraction take place between cation and anion that combine them together and is called ionic bond.

Example: Formation of Nacl sodium give one electron and chlorine gain one electron and both acquire noble gasses electronic configuration.                                                                         

Reaction: Na + Cl -----> NaCl   DH = -788 kJ/mol

Thus an anion bond does not form during formation of cation and anion but bond is formed when cation and anion combine to give a cystal.

Crystal Energy or Lattice Energy.

Amount of energy released when 1 mole of cation and anion are arrange in crystal lattice to form a crystal energy lattice energy.                                                                                                   

 Properties of Ionic Compound
1) Ionic compound are crystalline solids.
2) They have high melting point.
3) They have no molecules and are represented by emprical formula.
4) They have indefinite growth.
5) They are generally soluble in water.
6) They are not conductor of electricity in solid state but good conductor in solution form or molten state are called electrolytic conductors.

2) Covalent Bond:

Bond form by mutual sharing of electron between two atom s is called covalent bond.

Explanation:
Covalent bond is formed between two non metal atoms.Unpaired electron in the valance shell of atoms take part in covalent bond formation.In a covalent bond both the atoms of bond share electron to form bond.Electron pair of bond is called share pair or bond pair and it attracted by nuclei of both the atoms of a bond and is counted in both atoms.Thus in a covalent bond atoms acquire noble gas electronic configuration in the valance shell by the sharing of electrons.Covalent bond is represented by a solid line(----).This line represents shared pair of electrons.

H + H -------> H---H

Typs of Covalent Bond

There are three types of covalent bond.

1)Single Covalent Bond
Bond form by sharing of one pair of electrons between two atoms is called single covalent bond.A single covalent bond is formed if each atom of the bond shares one electron.

2)  Double Covalent Bond
Bond formed by sharing of three pair of electrons between two atoms is called double covalent bond.A double covalent bond id formed if each atom of the bond shares two electrons.

3)  Triple Covalent Bond
Bond formed by sharing of three pair of electrons between two atoms is called triple covalent bond.A triple covalent bond is formed if each atom of the bond share three electrons.

Properties Of Covalent Compound:
Covalent compounds are generally gasses and liquid.They exist in a molecules and are reprented by molecular formula.They are generally insoluble in water bur soluble in oganic solvent like sprit , benzene, ether etc.They are generally non conductors or bad conductors of electricity.

3)Co-ordinate Covalent Bond oR Dative Covalent Bond
Bond in which shared pair of electrons is denoted by one atom and accepted by other atom is called co-ordinate covalent bond or dative covalent bond.

Explanation
Atom of group IIIA like Al do not complete octet in valane shell after using all electrons of valance shell in bond formation.On the other hand atoms of group VA , VIA , VIIA like N , P , O , S , F , Cl , Br etc have lone pair of electrons in their valance shell after bond formation. A new bond is formed between two such atoms in which one atom has incomplete  octet and other which has lone pair of electrons.Atoms with lone pair donates its lone pai in sharing and the atom with incomplete octet accept that lone pair  to form bond called co-ordinate bond.

Definition Of Hydrides

  Hydrogen combines with other elements and forms binary compounds which are called Hydrides. Hydrogen forms binary compounds with all types of elements metals and non-metals excluding noble gases. Hydrides are classified into six major groups on the bases of nature of chemical bonding i.e (a) ionic hydrides (b) covalent hydrides (c) complex hydrides (d) Matallic hydrides (e) polymeric hydrides (f) Border line hydrides.

A) Ionic Hydrides:

       These types of hydrides are formed by the metals of IA group (alkali metals) and IIA group (alkaline earth metals) except Beryllium and Magnesium. In these hydrides, metal atoms acquire positive iob by losing valence electrons and hydrogen acquire negative ion by gaining the electron in the order to complete their shells, therefore these hydrides are known as "Ionic Hydrides". Also they possess salt like character, therefore they are called salt like or saline hydrides . They are strong reducing agent.

Preparation Of Ionic Hydrides:-
They are stable toward heat but their stability decreases in grouo from top to bottom. They are colourless, non-volatile and solublr in water but insoluble in organic solvents. They produce hydrogen gas when react with water, acids and alcohols, generally CaH2 is used to prepare hydrogen gas. Reaction with acids, water and alcohol are vigorous with hydrides of alkali-metals than alkaline earth metals.

B) Covalent Hydrides:

P-block elements, excluding noble gases, form covalent hydrides with hydrogen. The nature of chemical bond is covalent therefore they are known as covalent hydrides. They can be prepared by various methods e.g hydrogen when ignited with oxygen formed water and H2S gas is formed when sulphur is heated at 450 celsous and HCL is formed in sunlight as given under:

Preparation 
1) H2 + Cl2 ----> 2HCL
2) ‎H2 + S ----> H2S
3) ‎CaC2 + 2H2O ----> Ca(OH)2

Properties
i) They are colourless gases or volatile liquids with low boiling points except water which has higher boiling point i.e 100 celsius due to polarity.
ii) Hydrides of IIIA $ IVA group members are neutral e.g CH4 and BH3 etc
iii) Hydrides of VA group member are basic in nature e.g NH3 , PH3 etc while hydrides of VIA $ VIIA group members are acidic in nature and their acidity increases from left to right top to bottom e.g Acidic strenght in ascending order is H2O < H2S < SeH2.

C) Complex Hydrides:

Hydrides of IIIA grouo members are unstable except BH2. When hydrides of IA and IIIA elements combine each other complex hydrides are formed, as they possessing all three types of chemical bonds therefore they are complex. Their general formula is ABH4 where 'A' represents univalent alkali metals while 'B' indicates trivalent IIIA elements.

Properties:
These compounds are salt like while solids, stable up to 300 celsius They are soluble in water in which they ionize ti give Li and AlH4 ions AlH4 ions immediately reacts with water to produced hydrogen as
NaAlH4 + H2O ----> Al(OH)3 + NaOH + H2

Metalic Hydrides:

 They are also known as 'interstitial hydrides' or 'Non-stoichiometric' or Non-chemical hydrides b/c hydrogen forms hydrides of intermediate composition with transition metals by penetrating the crystal lattice structure of these metals without any chemical composition. Interstitial means empty space. Atomic hydrogen is obtained on heating such hydrides due to this characteristic they are used as 'Reducing Catalyst' or hydrogenation catalyst e.g platinum, Palladium and Nickel.
 ‎

E) Polymeric Hydrides:

Hydrides of (BeH2) and  (MgH2) of IIA group elements are polymerized with each other therefore they are known as polymeric hydrides. Their properties are intermediate b/w ionic hydrides and covalent hydrides.

F) Border Line Hydrides:-

These hydrides are formed by metals of IB, IIB and with the few members of IIIA such as Indium and thallium. Their properties are the intermediate between the metallic and covalent hydrides.

Isotopes:-

The existance of isotopes of elements was first discover by the J.J Thomson in (1912-1913). Isotopes are defined as
(i) Atoms of the same elements having same atomic structure but different atomic mass.
(ii) Atoms that have the same number of protons but different number of neutrons in their respective nuclei.

Isotopes Of Hydrogen:-

Protium or Ordinary Hydrogen:
It is an ordinary form of hydrogen. It is represented by H or P. It contains one proton in the nucleus and one electron in Is orbital. Its atomic number is one and mass number is also one. It is naturally free occuring hydrogen in the form of compounds with other element contain about 99.98% protium. Electronic structure of protium is:
1 = electron
1 = proton
0 = neutron.
Deutrium:-
It is the heavy hydrogen. It is represented by the H2 Or D2. It contain one proton and one neutron. Its atomic number is one and mass number is two. It is present in naturally occuring hydrogen about 0.0156% i.e in ratio is 1:15000. The existance of heavy hydrogen by Birge and Menzel in 1931. Electronic structure of Deutrium is:
1 = Electron
1= Proton
1= Neutron.

Tritium:-
It is the heaviest form of hydrogen and rarely occure in nature. It has one atomic number and three atomic mass. Electronic structure of Tritium is:
1= Electron
1= Proton
2= Neutron.

           

           

Position Of Hydrogen In Periodic Tables:-

The position of Hydrogen in periodic table is yet unsolved problem. It is placed above IA (alkali metals). IVA (Carbon family) and VIIA (halogen family) due to resemblance at small extent. It does not resemble completely with the members of any these groups elemenrs. The different behaviour of hydrogen can be explaining the fact that, it contains only one electron in its shell and only one proton in the nucleus with absence of neutron.

Comparison With Alkali Metals:-

Similarities:- like alkali metals, hydrogen possessing one electron in 's' orbital i.e both belong to s-block in respect of electronic configuration, both are monovalent and in electrolysis, both are deposited on cathode.
Dissimilarities:- Hydrogen is a gas, non-metal, does not exist in H state like Na etc. It can exist only in solvent form as Hydronium ion.

Comparison With Carbon Family:-

Similarities:
Like carbon family hydrogen has half filled electronic configuration in valence shell and some thermodynamics properties are also similar as ionization potential and electron affinity. Both carbon and hydrogen have close association in organic compounds.
Dissimilarities:
Hydrogen is a gas monovalent, non-metal, having 's' orbital in valence shell while carbon family is tetra-valent exist in solid state and their valence shell possessing 's' and 'p' orbitals.

Comparison With Halogen Family:-

Similarities:
Like halogen family hydrogen is diatomic gas, monovalent and gaints one electron from metal and become hydride, both are non-metals.
Dissimilarities:
Hydrogen can not exist as H positive like halogens and its electron affinity is also much less than those of halogens.

Conclusion:

In the light of above facts, hydrogen does not completely suit with members of any one group. Its exact position still undecided.

Industrial Preparation oF Hydrogen:

 i)From Electrolysis oF Water:
 ‎When ekectric curreent pass through water  containing some electrolyte (acid , base and salt) water decomposes into hydrogen and oxygen gas on electrolysis , hydrogen gas collected at cathode.
 ‎2H2O -----> 2H2 + O2
 ‎ii) Steam and Hydrocrbon Process
 ‎This process is also called oxidation of methane.
 ‎A mixture of natural gas and steam on heating at 900 C in presence of nickel catalyst , produce a mixture of CO and H2 commanly known as "water gas" as
 ‎CH4 + H2O ---->[3H2 + CO]
 ‎iii) By The Action oF Steam On Coal(coke) :
 ‎When steam is passed over red hot coke at 1000C, water gas is formed. It is an oxidation reaction.
 ‎C + H2O ----> H2 + CO
 ‎Separation oF Hydrogen Gas From Water Gas:
 ‎Mathod 1:  When water gas is passed over red hot iron at 500C mixture of CO2 gas dissolve in water leaving behind free hydrogen gas.
CO + H2 + H2O ------> CO2 + 2H2

Method 2: When water gas is cooled at -200 celsius with liquid air, CO becomes liquid and free hydrogen gas is obtained. Traces of CO from contaminated hydrogen can be removed by passing it through NaOH, where CO is absorbed by NaOH and HCOONa is obtained.

CO + NaOH -----> HCOONa

iv) Steam With Methanol Process (Oxidation Of Methanol):
When the mixture of methyl alcohol (wood spirit) and steam is heated at 250 celsius, CO2 , H2 gas are formed as
CH2OH + H2O ----> CO2 + 3H2
Carbon dioxide gas is separated by passing the mixture through water under high pressure where, CO2 dissolved in water and free hydrogen gas is obtained.

v) Thermal Decomposition Of Hydrocarbon ( Pyrolysis Or Cracking):
Natural gas is heated at 700 celsius in the absence of oxygen; on decomposition carbon black and hydrogen gas are formed, carbon black is used as filler in tyres manufacturing, type writer carbon papers, dyes etc.
CH4 + C ----> C + 2H2

vi) Thermal Decomposition of Ammonia:
When liquid ammonia is heated at 1000 celsius in presence of catalyst, mixture of N2 and H2 gases are formed. When this mixture is cooled at -196 celsius, N2 gas becomes liquid leaving behind pure hydrogen gas as
2NH3 ----> N2 + 3H2.

Atomic Hydrogen: 

Ordinary hydrogen exist in diatomic state, therefore , it is called as molecular hydrogen. ' The product obtained as a result of dissociation of molecular hydrogen is known as atomic hydrogen'. Hydrogen is found in the combined state in the form of compounds, the most abundant compound is water.

Preparation of Atomic Hydrogen:

In 1912, Langmuir prepared atomic hydrogen by thermal decomposition of ordinary hydrogen Or by electrical dissociation of molecular hydrogen under reduce pressure.
i) Atomic hydrogen is prepared by heating molecular hydrogen at 5000 celsius as:
H2 + 104 k.cal ----> 2 [H]
ii) Atomic hydrogen can also be prepared when electric current is passed through gas under reduce pressure i.e 1mmHg -to-0.1mmHg.
H2 ---> 2[H]
Properties of Atomic hydrogen:-
  Atomic hydrogen is much more reactive than molecular hydrogen. Expected reaction of molecular hydrogen are only those in which more than this energy will not takes place spontaneously. For the reaction of atomic hydrogen there is no such condition.

Uses Of Atomic Hydrogen:-

Atomic hydrogen is used to produce atomic hydrogen torch to attain a temperture of 4000 to 5000 celsius which employed in welding aluminium alloys, high chromium and nickel steels. It is based on the fact that when a jet of hydrogen is passed through an electric arc set up between tungsten rods.

The tabular arrangement following aufbau principle is called long form periodic table.
The periodic table is sub-divided on the basis of electronic configuration. In periodic table the horizontal lines or rows are called periods. There are seven periodic in all explained as:



Period 1 (n = 1):-

There is only one energy level (k-shell) for the elements of this period. It is the shortest period and contains only two elements as Hydrogen and Helium with electronic configuration.



Period 2 (n = 2):-

There are two shells (k, L) for the elements of this period. It contain 8 elements from Lithium to Neon. It is called first short period.



Period 3 (n = 3):-

There are three energy level for the elements of this period ( K, L, M) for the elements of this period. It also contains 8 elements fron Na to Ar. It is called second short period.



Period 4 (n = 4):-

There are four energy levels ( k , L , M, N)

It contain 18 elements from K to Kr. It is called first long period.



Period 5 (n = 5):-

There are five energy levels ( k , L , M, N, O)

It contain 18 elements from Rb to Xe. It is called second long period.



Period 6 (n = 6):-

This period contains 32 elements from cs to Rn. This period include 2 elements of s-block, i.e Cs and Ba , 10 elements of d-block from La to Hg , 14 elements of f-block from ce to Lu , 6 elements of p-block from Tl to Rn.



Period-7 (n = 7):-

This periodic includes 2 elements of s-block Fr and Ra, 10 elements of d-block With configuration and 14 elements of f-block (Actinides series) i.e Th to Lr.

Groups:-

The vertical coloumn in the periodic table are called groups. The elements with similar electronic configuration show similar properties and are placed in one group. There are 8 groups for each family (i.e A&B).There are 18 vertical coloumn.

Periods:-

The repetation of similar chemical properties after certain fixed intervals is known as periodicity. The repetation in properties of elements in due to repetation of similar electronic configuration of outer most energy levels of elements after certain intervals.

Elements of periodic table have been divided into s, p , d and f blocks on the basis of electronic configuration.



A) Noble Gases:-

      In the periodic table, the noble gases are found at the end of each period in zero groups. These are also known as Inert gases of reference group. VIII A group consist on six gases having complete outer shell, therefore they do not react with any atom or molecule at normal comdition. They are colourless and diamagnetic. Except Helium all the noble gases posses octet confuguration.

B) Representative (Typical) Elements or Active Elements or Normal Elements:-

  All the elements of A sub-groups of the periodic table are called representative or typical elements. These including metals, non-metals and metalloids. These include elements of s and p block.

1) s-Block:-
  These are the elements in which last electron enter in the s sub-shell therefore they are known as s-block elements. This block consists of group IA (Li, Na, K, Rb, Cs and fr), also known as Alkali metals and group IIA (Be, Mg, Ca, Sr, Ba and Ra), also known as alkaline earth metals. All the elements of this block are electropositive.

2) p-Block:-
 IIIA to VIIIA group elements are known as p-block elements. These are the elements in which outer most electron enter in the p sub-shell. They have their general configuration. These are the thirty elements in p-block, among these one is liquid (i.e Br) nine are gases, ten are metals (poor) and ten are non-metals.

C) Transition Elements:-

3) d-Block Elements:-

  These are the elements in which outer most electron enter in the d sub-shell, there these elements are known as d-block elements. As they are situated between s block and p block therefore they are known as outer transition elements. IB to VIIIB group elements are known as d-block elements. There are four series of elements 4th is incomplete.

4) f-Block:-
  These are the elements in which extra electron enter in the f-orbital are called f-block elements. As they are situated between IIIB and IVB groups therefore they are also known as inner transition elements. They consist on two series of 14 elements i.e Lanthanides and Actinides series. These block allotted a number IIIB (other than IIIB of d-block).

Dobereiner's Trails Rule:-

  In 1829 J.W Dobereiner discover that if three elements are arranged in ascending order with respect to atomic masses and in such arrangement mass middle element is approximately the arithemtic mean of sum of masses of other two elements then they can show similar chemical properties. These are called Dobereiner's traids.

Newland's Law of Octave:-

An English chemist in 1864-1869 proposed another periodic law for classification of elements as " If elements are arranged in ascending order with respect to their atomic masses then properties of every eight element were similar to those of the first".

       

Mendeleev's Periodic Table:-

The present system of classification of elements is based upon the periodic law enunciated by a Russian Chemist Mendeleev. He found that if the element are listed in order of increasing atomic masses (ascending order) certain sets or properties are re-occur periodically. Mendeleev's periodic law is also known as the law of extension of Newland's law of octave. He stated this fact in the form of law in 1869 according to which :
         "The physical and chemical properties of elements are periodic function of their atomic masses.

Mendeleev's Periodic Table:-

In Mendeleev periodic table the element have been arranged in increasing order of their atomic masses in horizontal series in such a way that the elements having similar properties are placed in the same vertical column (groups). Mendeleev periodic table had no zero groups. Mendeleev periodic table is also known as short form periodic table.

Advantanges of Mendeleev's Periodic Table:-

A) Prediction of New Elements:
    There are many vacant spaces or groups in Mendeleev's periodic table.
The Mendeleev predicts the properties of unknwon elements that would occupy these spaces. The prediction was found correct after discoveries of these elements. For example the places for Scandium, Gallium and Germanium were left bank which were discovery later.

B) Correction of Doubtful Atomic Masses:
      Another advantages of using sequence of increasing masses is the correction of some doubtful atomic masses, for example the atomic masses of Beryllium was corrected from 13.5 to 9 with the mass of Beryllium was given the position between the Lithium and Boron.

C) Systematic Study of Elements:-
    Mendeleev's periodic table has helped the chemist to study the properties of elements more systematically. For example, the study of sodium metal helped the chemist to predict the properties of other alkali metals, similarly the study chlorine means to large extent the study of all halogens.

Disadvantages Of Mendeelev's Periodic Law and Periodic Table:-

A) Irregular Position Of Elements:
    When elements are arrange in order or ascending atomic masses Potassium should precede Argon, Nickel should precede Cobalt and Iodine should preced Tellurium but the correct position of elements in the perdioc table is that Argon precede Potassium, Cobalt precede Nickel and Tellurium precede Iodine.

B) Position of Isotopes:
Mendeleev periodic table does not give any position for isotope. If isotopes are placed in ascending order wity respect to atomic masses, the arrangement of other elements are disturb.

C) Position of Lanthanides And Actinides Series:

Lanthanides and Actinides are series of 14 elements each. These series have not been assign any place in the periodic table according to the periodic law.

D) Dissimilar Elements Are Placed In The Same Groups:

Alkali metals ( Lithium, Sodium, potassium, Rubidium and cesium and Francium) metals and coinage metals copper silver and Aurum which are differ widely in properties are placed in the same group. However this discrepancy has been removed later by placing them into two sub-group A family and B Family.

Mosley's Or Modern Periodic Law:-

In 1913 a British Physicist, Mosley found that atomic number is the fundamental properties of an atom instead of atomic mass. He proved beyond doubt that the properties of elements are well explained and most of their anomalies and defect of Mendeleev periodic table disappear if the basis of arrangement of element are changed from mass to atomic number. This formulate the modern periodic law state as:
            "The physical and chemical properties of element are the periodic function of atomic number" when the elements are arranged in the ascending order of their atomic number, the element possising similar properties are repeated at regular interval.

Modern Periodic Table:-

Interbation union of Pure and applied chemistry (IUPAC) recommended modern periodic table in 1984. In this periodic table the elements are arranged in the ascending order of their atomic number instead of their atomic masses, and for furthur development of atomic structure, modern periodic law may be state as:
   " The physical and chemical properties of elements are fuction of their electronic configuration of their atoms which vary with increasing atomic numbers in a periodic manner". Mosley's modern periodic table also known as long form of periodic table.
   ‎

Advantages Of Modern Periodic Law/Modern Periodic Table.

1) In modern periodic table the position of an element is releated to electronic configuration of its atom.
2) ‎There is gradual change in properties of element (i.e physical and chemical ) with increase in their atomic numbers.
3) ‎outer transition (d Block) and inner tranistion (f block) elements are aloted a situation between s block and p block.
4) ‎Metals and non-metals are completely separated to each other.
5) ‎The arrangement of atoms is easy to remember and re-produce.
6) ‎The greates advantages of modern periodic table is that this can be divided into four blocks s block p block d block and f block.
7) ‎Modern periodic table solve the problem of misfit pair or elements and position of rare earth elements (i.e lanthanides and actinides series)
8) ‎It has also solve the position of isotopes, since all the isotopes of elements have same atomic number, therefore they need only one place in the periodic table.

Region around the nucleus of an atom where probability of finding electron is maximum or where the electron density is maximun is called orbit or Energy level or shell.

Representation Of Orbits or Energy Levels or Shells:-

Bohr represented Orbits or energy levels or shell's by the capital letters of alphabet as K, L, M, N, O, P, Q shells.

Sub Orbit or Sub Energy Level or Sub Shell:-

Different spaces of an orbit or Energy level or shell where electron revolves with different energy are called sub orbits or sub energy levels or sub shelle. There are four orbits or sub energy levels or sub shells given below:
Four Sub orbits Sub energy levels or sub shells:-
• S- sub shell
• ‎p - sub shell
• ‎d - sub shell
• ‎f - sub shell
s stand for sharp
p stand for principle
d stand for diffuse
f stand for fundamental.

Orbitals:-

Orientation of a sub shell in space or directions of motion of electrons in space in a sub shell are called orbitals.
Orbital of  S- Sub Shell:-
There is one orbital of s- sub shell, which is spherical in shape.
Orbitals of  P- Sub Shell:-
There are three orbital of p- sub shell, which are called px, py and pz and are dumbbell in shape.
Orbitals of  d- Sub Shell:-
There are five orbitals of d-sub shell, which are dxy, dyz, dxz, dx^2y^2 and dz^2 difficult to give names of seven orbitals in three dimensional space.

Quantum Numbers:-

Numbers or integral which shows the behaviour of an electron in an atom are called quantum numbers. There are four quantum numbers which are given below:
1) Principle Quantum Number (n):
• Principle quantum numbers shows the number of orbitals and energy levels, size of shells and energy of shells. Greater the value of n larger the size of shell and more will be the energy.
• ‎Its shows the number of sub shell and sub energy levels in the shell or energy level, and it is equal to the value of n for a shell.
• ‎Value of n shows the number of electron to be filled in the shell of energy level it is equal to 2n^2

2) Azimuthal Quantum Number or Subsidiary Quantum Number (l) :-
• value of l is depend on the value of n its from the 0 to n-1.
• ‎value of l show the number of sub shell in a shell, thus for k, L, M and N value of l are (0), two (0,1), three (0,1,2) , four (0,1,2,3) so they have one (s) two (s,p) three (s,p,d) four (s,p,d,f).
• ‎Value of l is 0 for s, 1 for p, 2 for d, 3 for f sub shell.
• ‎value of l shows the number of electron to be filled in a sub shell. It is equal to l+2 thus in s we can fill 4(0) + 2 = 2 electrons, in p we can fill 4(1) + 2 = electrons, in d we can fill 4(2) + 2 = 10, in f we can fill 4(3) + 2 = 14 electrons.
• ‎Value of l shows number of orbitals in sub shell it is equal to 2l + 1. Thus s has 2(0) + 1 = 1 orbitals, p has 2(1) + 1 = 3 orbitals (px, py, pz), d has 2(2) + 1 = 5 orbitals and f has 2(3) + 1 = 7 orbitals.
3)Magnetic Quantum Number (m):
This quantum number shows the magnetic property of an element in an orbital under the influence of an external magnetic field. Its shows the number or orientations of a sub shell in space.
Value of (m):-
Value of m depened on the value of l and s  from +l to 0 to -l. Values of m for s, p, d and f are given below:
For s, l = 0 thus m = 0, for p, l = 1 thus m = +1, 0, -1, for d l = 2 thus m = +2, +1, 0, -1, -2 and for f, l = 3 thus m = +3, +2, +1, 0, -1, -2, -3.
4) Spin Quantum Number (s):
This quantum number shows the spin of an electron in an orbital. If there is one electron in an orbital than 50% probability for it is to spin clockwise and 50% to spin anticlock wise, so value of s for it is +1/2 or -1/2. But if there are two electrons in an orbital then always one spins clockwise and other anticlock wise, so the value of s for one electron is always +1/2 and for other always -1/2.

Paulli's exclusion Principle:-

Definition:-
No two electron in an orbital have same values of all the four quantum numbers.
Expanation:-
According to Paulli's exclusion principle if two electron are present in the same orbital then they can not have same values for all the four quantum numbers.
They have same values of first three quantum numbers which are for the orbital, but always value of fourth spin quantum number is different because one electron move clock wise and other moves anticlock wise.

This principle for the factor affecting the balance of chemical equilibrium.Le chatelier principle deacribe the factor which affect the balance of chemical equilibrium.

DEFINITION:
 If a stress is applied on a reaction at equilibrium then reaction changes it's direction reduce the effect of that stress.

EXPLANATION:-
 If a stress is applied on a reaction at equilibrium by changing some factor like concentration , temperature , pressure then it will disturb the balance of chemical equilibrium, and the reaction change it's direction either forward or backward to reduce effect of that stress and acquire equilibrium again.
Effect of diferent factiors on the balance of chemical equilibrium is given below.

1)Effect OF CHANGE IN CONCENTRATION:-
At equilibrium if the concentration of reactants increased then it will disturb the equilibrium and the reaction will take place forward direction to acquire equilibrium again.If the concentration of product is increase then it will also disturb the balance of equilibrium and the reaction will take place in backward direction to acquirw equilibrium again.

2)EFFECT OF CHANGE IN TEMPERATURE:-

i)EFFECT OF CHANGE IN TEMPERATURE ON EXOTHERMIC REACTION:-
In exothermic reaction heat is released in forward direction and absorbe in backward direction.If the temperature is increase then heat will absorb so reaction goes to backward direction. If the temperature is decreased then heat will release so the reaction goes to forward direction.

ii)EFFECT OF CHANGE IN TEMPERATURE ON ENDOTHERMIC REACTION:-
In an endothermic reaction heat absorbed in forward direction and released in backward direction.If temperature is increased then heat will absorb so the reaction goes to forward direction.If the temperature is decreased then the heat will released so the reaction goes to backward direction.

3)EFFECT OF CHANGE IN PRESSURE:-
Pressure effect only gaseous equilibrium.Three types of reactions are affected by pressure.

i) REACTION BY INCREASE OF VOLUME:-
If the pressure is increased then it will disturb the equilibrium and reaction goes to forward direction where volume is decreased.If pressure is decreased then it will also disturb the equilibrium and the reaction goes to forward direction where volume is increased.

ii)REACTION BY DECREASE IN VOLUME:-
If pressure is increase then it will disturb the equilibrium and reaction goes to forward direction where volume is decreased.If the pressure is decreased then it will also disturb the equilibrium and reaction goes to backward direction where volume is increased.

iii)REACTION BY SAME VOLUME:-
Change of pressure has no effect on this equilibrium.

4)EFFECT OF CATALYST:-
Catalyst has no effect on the balance of chemical equilibrium.Catalyst only changes the rate of reaction.

INDUSTRIAL APPLICATION OF LE CHATELIER's PRINCIPLE:-
Important industrial application of Le Chatelier's principle are given below.

1)TO HABBER's PROCESS IN PREPARATION OF NH3 GAS:-
By habber's process NH3 gas is prepared by the reaction:
N2 + 3H2<===>2NH3+46.2kJ/mol
This reaction is exothermic and take place by decrease of volume.
Affect of different factors on it is given below.

i)EFFECT OF CHANGE IN CONCENTRATION:-
At equilibrium if the concentration of reactant N2 and H2 is increased then it will disturb the equilibrium and according to Le Chatelier principle reaction goes to forward direction and gives more product NH3.

ii)EFFECT OF CHANGE IN PRESSURE:-
As the reaction take place by decrease in volume, So if pressure is increased then it will disturb the equilibrium and according to Le Chatelier's principle the reaction take place in forward direction where volume is decreased and give more product NH3.
In order to obtain maximum product reaction take place at 450-500 atm pressure.

iii) EFFECT OF CHANGE IN TEMPERATURE:-
As reaction is exothermic so if the temperature is decreased then according to Le Chatelier's principle heat will be realesed and reaction goes to forward direction and gives more product NH3.
But actually in industry the reaction is carried out at high temperature at 500 degree calcius in presence of iron oxide catalyst which give reduce product but very high rate.

2)TO CONTACT PROCESS IN THE PREPARATION OF SO3 GAS:-
For formation of sulphuric acid by contact process SO3 gas is prepared by reaction:
2SO2+O2<===>2SO3 +395KJ/mol
This reaction is exothermic and take place by decreased in volume.
Affect of different factor on it is below:

i)EFFECT OF CHANGE IN CONCENTRATION:-
At equilibrium if concentration of reactant is increase then it will disturb the equilibrium and according to Le Chatelier's principle the raction goes to forward direction and give more product SO3.

ii)EFFECT OF CHANGE IN PRESSURE:-
As the reaction take place by decrease in volume,So if temperature is increase then it will disturb the equilibrium according to Le Chatelier's principle reaction take place goes to forward direction where volume is decreased and give more product SO3.
In order to obtain maximum product reaction should be take place at 450-500 atm pressure.

iii)EFFECT OF CHANGE IN TEMPERATURE:-
As the reaction is exothermic so if the temperature is decreased then according to Le Chatelier's principle heat will be released and reaction take place goes to forward direction and gives more product SO3.
But actually in industry the reaction is carried out at high temperature up to 500 degree calcius in the presence of vanadium penta oxide catalyst which gives reduce product but at very high rate.