Oxyacids of NitrogenNitrous acid, Nitric acid, Hyponitrous acid

Oxyacids of Nitrogen:a. Nitrous acid - HNO2

b. Nitric acid - HNO3

c. Hyponitrous acid - H2N2O4

a. Nitrous Acid: HNO2

Preparation: 

i. By dissolving N2O3 in water

N2O3 + H2O   2HNO2

By action of acid on metallic nitrites

NaNO2 + HCl   NaCl + HNO2

 ii. By oxidation of NH3

NH3 + 3H2O2   HNO2 + 4H2OProperties: 

iii. It is a weak acid and does not exist in free state. 

iv. 2HNO2   NO + NO2 + H2O (Vapour phase)

3HNO2   HNO3 + H2O + 2NO (Aqueous solution) 

v. Oxidising property

2HNO2  2NO + H2O + [O]

H2S + [O]   H2O + S

SO2 + H2O + [O]   H2SO4

2FeSO4 + H2SO4 + [O]   Fe2(SO4)3 + H2O

SnCl2 + 2HCl + [O]   SnCl4 + H2O

2Kl + H2O + [O]   2KOH + l2 

vi. Reducing property

HNO2 + [O]   HNO3

K2Cr2O7 + 4H2SO4 + 3HNO2   K2SO4 + Cr2(SO4)3 + 3HNO3 + 4H2O

2KmnO4 + 3H2SO4 + 5HNO2   K2SO4 + 2MnSO4 + 3H2O + 5HNO3

Br2 + H2O + HNO2   HNO3 + 2HBr 

vii. H2NCONH2 + 2HNO2   CO2 + 2N2 + 3H2O

 b. Nitric acid: HNO3

Preparation:

i.  By heating sodium nitrate with conc. sulphuric acid.

2NaNO3 + H2SO4   2HNO3 + Na2SO4 

ii. Birkeland - Eyde Process

N2 + O2   2NO

2NO + O2   2NO2

3NO2 + H2O   2HNO3 + NO 

iii. Ostwald's Process -

4NH3 + 5O2   4NO + 6H2O

2NO + O2   2NO2

3NO2 + H2O   2HNO3 + NO

Structure:  

Properties:

Anhydrous acid is a color less fuming liquid.It usually acquires yellow color due to its decomposition by sunlight into NO2.

4HNO3   4NO2 + 2H2O + O2

C12H22O11 + 18[O]   6H2C2O4 + 5H2O

Reaction with Metals 

iv. Mg + 2HNO3 (dil)   Mg(NO3)2 + H2

 v. 3Mg + 8HNO3 (conc.)   3Mg (NO3)2 + 4H2O + 2NO

 vi. 3Cu + 8HNO3 (cold and dilute)   3Cu(NO3)2 + 4H2O + 2NO

 vii. Cu + 4HNO3 (cold and conc.)   Cu(NO3)2 + 2H2O + 2NO2

[Ag, Pb and  Bi also react as Cu] 

viii. 6Hg + 6HNO3 (dilute)   3Hg2(NO3)2 + 4H2O + 2NO 

ix. Hg + 4HNO3 (conc.)   Hg(NO3)2 + 2H2O + 2NO2

 x. 4Zn + 10HNO3   4Zn(NO3)2 + NH4NO3 + 3H2O

(very dilute) 

xi. 4Zn + 10HNO3 (dil)   4Zn(NO3)2 + N2O + 5H2O 

xii. 4Fe + 10HNO3   4Fe(NO3)2 + NH4NO3 + 3H2O(very dilute)

 xiii. 4Sn + 10HNO3   4Sn(NO3)2 + NH4NO3 + 3H2O

(dil.) 

xiv. Fe + 6HNO3   Fe(NO3)3 + 3NO2 + 3H2O (conc.)

 xv. Sn + 4HNO3   H2SnO3 + H2O + 4NO2

(conc.)Reaction with non-metals, metalloids and compounds

xvi. C + 4HNO3   CO2 + 4NO2 + 2H2O 

xvii. S + 6HNO3   H2SO4 + 6NO2 + 2H2O 

xviii. l2 + 10HNO3   2HIO3 + 10NO2 + 2H2O 

xix. B + 3HNO3   H3BO3 + 3NO2

 xx. As + 5HNO3   H3AsO4 + 5NO2 + H2O

 xxi. Sb + 5HNO3   H3SbO4 + H2O + 5NO2

 xxii. SO2 + 2HNO3   H2SO4 + 2NO + O2

 xxiii. 2Hl + 2HNO3   2NO2 + 3l2 + 2H2O

 xxiv. 6FeSO4 + 3H2SO4 + 2HNO3   3Fe2(SO4)3 + 2NO + 4H2O

Oxyacids of PhosphorusHypophosphorus acid, Phosphorus acid, Orthophosphoric acid, Metaphosphoric acid, Hypophosphoric acid, Pyrophosphoric acid

Oxyacids of Phosphorus:i. Hypophosphorus acid - H3PO2

ii. Phosphorus acid - H3PO3

iii. Orthophosphoric acid - H3PO4

iv. Metaphosphoric acid - HPO3

v. Hypophosphoric acid - H4P2O6

vi. Pyrophosphoric acid - H4P2O7

a. Phosphorus acid - Orthophosphorus acid - H3PO3

Preparation: 

i. Phosphorus trichloride when reacted with water gives phosphorus acid.

PCl3 + 3H2O   H3PO3 + 3HCl

ii. Phosphorus trioxide (P4O6) on reaction with water gives phosphorus acid.

P4O6 + 6H2O   4H3PO3

Properties: 

iii. Phosphorus acid disproportionates to give PH3 and H3PO4.

4H3PO3   3H3PO4 + PH3

iv. Phosphorus acid is a disbasic acid.

H3PO3    H+ + H2PO3-

H2PO3-    H+ + HPO3

-2

v. Phosphorus acid on reaction with phosphorus pentachloride gives phosphorus oxychloride.

H3PO3 + 3PCl5   PCl3 + 3POCl3 + 3HCl

b. Orthophosphoric Acid - H3PO4

Preparation:i. Phosphorus when treated with nitric acid gives H3PO4.

P4 + 20HNO3   4H3PO4 + 20NO2 + 4H2O

ii. Calcium phosphate on reaction with sulphuric acid gives H3PO4

iii. Ca3(PO4)2 + 3H2SO4   2H3PO4 + 3CaSO4

iv. Phosphorus on reaction with excess of oxygen gives oxide which on further reaction with hot water gives orthophosphoric acid.

P4 + 5O2   P4O10     4H3PO4

Properties: 

v. Orthophosphoric acid is a tribasic acid and forms series of salts.

Primary phosphate - NaH2PO4

Secondary phosphate - Na2HPO4

Tertiary phosphate - Na3PO4

vi. 2H3PO4      H4P2O7 + H2O

vii. H3PO4      (HPO3)n + H2Ometaphosphoric acid

viii. H3PO4 on reaction with BaCl2 and AgNO3 gives precipitate.

3BaCl2 + 2H3PO4   Ba3(PO4)2 + 6HClWhite ppt

3AgNO3 + H3PO4   Ag3PO4 + 3HNO3(yellow)

ix. On heating H3PO4 in presence of nitric acid with ammonium molybdate, a canary yellow precipitate of ammonium phosphomolybdate is formed. (test of Po4

3- ion)

H3PO4 + 21HNO3 + 12(NH4)2MnO4   (NH4)3PO4 . 12MoO3 + 21NH4NO3 + 12H2O

Phosphorus (P)Phosphorus is second number of the "Nitrogen family" with group number 15 and period number 3

Phosphorus (P)Phosphorus Atomic Number : 15Phosphorus Atomic Mass : 31Phosphorus Electronic Configuration : [Ne]3s23p3

Phosphorus Group Number : 15 (V A)Phosphorus Period Number : 3Phosphorus Relative Abundance : 11Phosphorus is second number of the "Nitrogen family" with group number 15 and period number 3. Phosphorus is mostly used in match industry.

Occurence of Phosphorus

phosphorus being an active element, it is not found free in nature. Phosphorus occurs as phosphate in the rocks and in the soil.The important minerals of phosphorus are

i. Phosphorite - Ca3(PO4)2

ii. Flourapatite - 3Ca3(PO4)2.CaF2

iii. Chlorapatite - 3Ca3(PO4)2.CaCl2Other than this, phosphorus is essential constituent of bones, teeth etc. Bone ash contains about 80% of calcium phosphate.

Properties of Phosphorus:1. Phosphorus is a non-metal.

2. Phosphorus though a solid can also convert easily into vapour state.

3. The atomic radius of phosphorus (1.10 ) is higher than nitrogen (0.74 ) and lower than the rest of the family members

4. The first ionisation energy of phosphoprus (253.9 kcal) is lower than nitrogen (336) due to its own bigger size than nitrogen and higher than the rest of the family members

5. Electronegativity of phosphorus (2.1) is lower than the nitrogen but higher than the rest of the members.

6. Phosphorus can exist in discrete tetratomic tetrahedral molecule i.e. P4.

7. Phosphorus can exists in number of allotropic forms like

i. White or yellow phosphorus

ii. Red phosphorus

iii. Scarlet phosphorus

iv.  - Black phosphorus

v.    - Black phosphorus

vi. Violet phosphorus

8. Phosphorus can show oxidation state of -3 to +5

Ammonia - HNO3Ammonia Preparation and Ammonia PropertiesAmmonia: HNO3

Preparation:i. From Ammonium Salts

2NH4Cl + Ca(OH)2   CaCl2 + 2NH3 + 2H2O

ii. From nitrides 

Mg3N2 + 6H2O   3Mg(OH)2 + 2NH3

iii. Haber's Process

N2 + 3H2   2NH3

iv. Cyanamide Process

CaC2 + N2   CaCN2 + C

CaCN2 + 3H2O   CaCO3 + 2NH3

v. Serpeck's Process

Al2O3 + 3C + N2   2AIN + 3CO

AlN + 3H2O   Al(OH)3 + NH3

Properties: 

i. 4NH3 + 3O2   2N2 + 6H2O

4NH3 + 5O2   4NO + 6H2O

ii. 8NH3 + 3Cl2   N2 + 6NH4Cl

iii. NH3 + 3Cl2   NCl3 + 3HCl

iv. 2Na + 2NH3   2NaNH2 + H2

v. Ag+ + 2NH3   [Ag(NH3)2]+

vi. Cu2+ + 4NH3   [Cu(NH3) 4]+2

vii. 2K2Hgl4 + NH3 + 3KOH   H2N.HgO. Hgl + 7Kl + 2H2O(Brown ppt)

 HgCl2 + 2Kl   2KCl + Hgl2

Hgl2 + 2Kl   K2Hgl4Nessler's Reagent

Isolation of SulphurSulphur can be isolated from Frasch Process

Isolation of Sulphur

Sulphur can be isolated from1. Frasch Process

 2. As by product from

 i. Alkali waste of Le Blanc's process

ii. Spent oxides of gas works

iii. Iron pyrites1. Frasch Process:

i. Three concentric pipes are sunk deep into under ground.

ii. Super heated water at around 170 C forced into pipe where sulphur is melted.

iii. Compressed air from inner pipe allows sulphur as liquid to come on the surface which further solidified as 99% pure sulphur.

 2. As By product from:

i. Alkali waste 

CaS + H2O + CO2   CaCO3 + H2S

2H2S + O2   2H2O + S

ii. Spent oxides of Coal gas

2Fe2S3 + 3O2  2Fe2O3 + 6S 

iii. Iron pyrites

3FeS2   Fe3S4 + 2S

3FeS2 + 5O2   FeO4 + 3SO2 + 3S

FeS + CO2   FeO + CO + S

Sulphur (S)Sulphur is the sixteenth most abundant element on earth crust

Sulphur (S)

Sulphur Atomic Number : 16Sulphur Atomic Mass : 32Sulphur Electronic Configuration: [Ne]3s23p4

Sulphur Group Number : 16 (VlA)Sulphur Period Number : 3Sulphur Relative Abundance : 161. Sulphur is the sixteenth most abundant element on earth crust. It constitutes 0.034% by weight of the earth's

crust. 

2. Sulphur is the p-block element and is the second member of "Chalcogen family" after oxygen. 

3. The group number of sulphur is 16 and period number is 3. 

4. Sulphur is the mostly used in manufacture of SO2, H2SO4, fire works, medicine.Properties of Sulphur1. Sulphur exist as staggered 8-atom ring S8 molecule. Each sulphur atom is in sp3 -hybridised state.

 2. Sulphur is a non metal.

 3. The atomic radius, atomic volume and density of sulphur is higher than oxygen but lower than rest of the

family members. 

4. Electronegativity of sulphur is lower than that of oxygen but higher than rest of the family members. 

5. Melting point and boiling point of sulphur are higher than the oxygen due to its bigger size than oxygen but lower than rest of the chalcogen members 

6. Catenation property is more pronounced in sulphur as compared to rest of the family members. 

7. Sulphur can exhibit the range of -2 to +6 oxidation state due to availability of vacant d-orbital. 

8. Sulphur reacts with acid where it itself gets oxidised.

S + 2H2SO4 (Conc.)   3SO2 + 2H2O

S + 6HNO3 (Conc.)   H2SO4 + 6NO2 + 2H2O

4S + 6NaOH   2Na2S + Na2S2O3 + 3H2O 

9. Sulphur undergoes reduction in presence of hydrogen.

H2 + S   H2S 

10. Cl2 + 2S   S2Cl2 

11. C + 2S   CS2

 12. 2As + 3S   As2S3

 13. 2H2O (steam) + 3S (boiling)   2H2S + SO2

Oxygen (O)Oxygen is 46.6% by weight in the earth's crust

Oxygen (O)Oxygen Atomic Number : 8Oxygen Atomic Mass : 16Oxygen Electronic Configuration : [He]2s22p4

Oxygen Group Number : 16 (VlA)Oxygen Period Number : 2Oxygen Relative Abundance : 1Oxygen is a most abundant element on earth. Oxygen is 46.6% by weight in the earth's crust. In atmosphere, oxygen is present 21% by volume.

Oxygen is the first member of "Chalcogen family".

Properties of Oxygen1. Oxygen is a gas while other family members are solids.

2. Oxygen molecule is diatomic while the other family members exist in polyatomic ring form.

3. Oxygen is non-metal whereas metallic character increases down the group. The non-metallic character of oxygen is due to its high value of electronegativity.

4. Oxygen molecule is highly stable due to higher bond energy of multiple bonds.

5. The atomic radius; atomic volume and density of oxygen are lower than rest of the family members.

6. The ionisation energies of oxygen due to its smaller size is very high compared to that of the other family members.

7. Oxygen is highly electronegative member of its family. It is the second most electronegative element after fluorine (4).

8. The melting point -219 C and boiling point -183 C of oxygen are lower than that of other family members.

9. Oxygen mostly exhibits oxidation state of -2. Oxygen do not have d-orbital hence can't show +4 +6 oxidation state while other family members can.

10. Oxygen reacts with metal to form basic oxide.

K + O2   KO2 (Potassium super oxide)

2Mg + O2   2MgO (Magnesium oxide)

11. It reacts with non-metal to form acidic oxide.

C + O2   CO2

S + O2   SO2

4P + 5O2   P4O10

12. It reacts with some metals to form amphoteric oxides (acidic as well as basic)

4Al + 3O2   2Al2O3

2Be + O2   2BeO

2Zn + O2   2ZnO

13. It reacts-with some non-metals to form neural oxide

C +   O2     CO

N2 + O2   2NO

14. It acts as oxidising agent. It is trequired for combusion. It is used for roasting of sulphide ores.

CS2 + 3O2   CO2 + 2SO2

2ZnS + 3O2   2ZnO + 2SO2

Isolation of Oxygen & Compounds of OxygenOxygen is pale blue gas having a strong characteristic smell. It is neutral to litmus

Isolation of Oxygen:

In laboratory it is prepared by heating  KMnO4 or KClO3 in presence of MnO2.

2KClO3 (s)   2KCl + 3O2

2KMnO4   K2MnO4 + MnO2 + O2

It can also be prepared by reaction of H2O on Na2O2

2Na2O2 + 2H2O(l)   4NaOH + O2

On large scale it is prepared by fractional distillation of liquid air.

Pure oxygen is prepared by electrolysis of water.

Oxygen is also manufactured byi. Brine's Process:

BaO is heated at 500 C in air. It is converted into BaO2, which on further increase in temperature upto 800 C decomposes to give oxygen. 

ii. By electrolysis of water:Electrolysis is done by using alkaline water using nickel or platinum electrode which gives hydrogen and oxygen. 

Compounds of Oxygen:

Ozone - O3:

Preparation:

It is prepared by subjecting pure oxygen to silent electric discharge

3O2   2O3       H = + 284.5 kJ mole-1

Properties:

It is pale blue gas having a strong characteristic smell. It is neutral to litmus.

1. O3    O2 + O 

2. H2S + O   H2O + S 

3. 2Ag + O   Ag2O 

4. 2Hg + [O]   Hg2O 

5. l2 + H2O + 5[O]   2HIO3

 6. S + H2O + 3[O]   H2SO4

 7. 2P + 3H2O + 5[O]   2H3PO4

 8. It is better oxidising agent as compared to H2O2.

H2O2 + O3   H2O + 2O2

BaO2 + O3   BaO + 2O2

It is condensed to blue liquid (Boiling point 161.2 K)

It condenses to a violet-black solid (m. pt 80.6 K), Ozone has angular structure. Both the O-O bonds are of equal bond length due to resonance.

 

Test of Ozone

In presence of O3, mercury loses its meniscus and starts sticking to glass. This is known as telling of mercury.

It does not release iodine from Kl in presence of FeSO4. In this way it is different from H2O2.

Hydrogen BondingType of H-Bonding, Modern Concept of Covalent Bonding

In formed when H-atom of one molecules combines with the electronegative atom of other molecule by dipole-dipole interaction (N, O, F and   electron cloud exhibit H-bonding)

Type of H-Bonding1. Intermolecular H-Bonding: Formed between H and electronegative element of two different or same

molecule

It increase the boiling point, solubility in water and viscosity. 

2. Intramolecular hydrogen bonding: Formed between H and electronegative element present in the same molecule.

 3. It increases volatile nature, decreases boiling point and solubility.Modern Concept of Covalent Bonding

Valence bond theory: Formed by overlapping of half filled atomic orbitals.

Main Characters:1. Greater the overlapping higher the strength of the bond.2. Electron density is maximum between the two atom where overlapping takes place.3. p-orbitals will form stronger bond than s-orbital.4. When overlapping of orbital takes place along their axis the bond formed is (sigma) bond.5. When overlapping of orbital takes place laterally or sidewise the bond formed is bond.

HybridizationHypothetical concept of hybridization is introduced

The VBT theory fails to explain shape of the molecules. So hypothetical concept of hybridization is introduced. According to this any number of atomic orbitals of the atom which differ in energy with each other to form new orbital called hybrid orbital.

It only includes bond (along with lone pair).

V = No. of valence shell electrons in ground state to central atom.G = No. of monovalent atom attached to central atom.a = Magnitude of charge on anion.c = Magnitude of charge on cation.

H value Hybridization Shape of molecule Bond angle2 sp Linear 1803 sp2 Plane triangular 1204 sp3 Tetrahedral 109  284 dsp2 Square planar 905 sp3d or dsp3 Trigonal bipyramidal 120  & 906 sp2d2 or d2sp3 Octahedral bipyramidal 907 sp3d3 or d3sp3 Pentagonal bipyramidal 72  & 90

Chemical BondingCause of Chemical Bonding & Type of BondingChemical Bond is defined as the force that acts between two or more atoms to hold them together as a stable molecule.

Cause of Chemical Bonding1. To decrease potential energy2. To complete octet or dupletType of Bonding1. Electrovalent or Ionic Bonding: Formed by the transfer of one or more electrons from one atom to another

atom.

Conditions: large cation + small anion + low charge on ions (Also called Fajan's rule)

Characteristics of ionic compounds

i. Crystalline in natureii. Have high melting and boiling pointiii. Do not conduct electricity in solid state but conduct electricity in molten state and in aq. medium.iv. Soluble in polar solvent like water.

2. Covalent Bond: Formed by mutual sharing of electrons between two or more atoms, it may be single, double or triple bond.

Polar and non-polar Covalent bonds

XA - XB 0 the bond is polar covalent bond.

XA - XB 0 the bond is non-polar covalent bond.

Characteristics of Covalent Compounds

i. Generally exist as gases or liquids under normal condition of temperature and pressure.ii. Bad conductor of electricity.iii. Insoluble in polar solvent like water but soluble in non-polar solvent.iv. Generally low melting and boiling temperature than ionic compound.

Co-ordinate or Dative CompoundFormed when shared pair of electrons, is contributed by one of the two atoms. The bond is represented by an arrow

Characteristics of Co-ordinate CompoundHave higher melting and boiling points than purely covalent compounds.

They are sparingly soluble in polar solvent like water but readily soluble in non-polar solvents.Molecular Orbital Theory

According to this theory all the atomic orbitals of the atom participating in molecule formation get disturbed when the concerned nuclei comes closer. They all get mixed up to give rise to an equivalent number of new orbitals that belong to the molecules.

Linear Combination of Atomic Orbitals (LCAO)1. Overlapping of atomic orbitals is the overlapping of waves.

2. In phase overlapping results in Bonding molecular orbital and out of phase over lapping results in anti bonding molecular orbital.

3. Energy levels of these orbitals is increasing energy sequence is

 1s <  * 1s <   2s <  * 2s <   2pz <   2px =    2py <  * 2px =  * 2py <  * 2pz for O2, F2 and Ne2 molecules

Note: For B2, C2, N2 molecules, E 2px = E 2py < E σ2pz

Bond Order

Higher the bond order smaller the bond length

B. Order Stability (Molecule)< 0 Unstable and does not exist= 0 Does not exist0.5 Exist but unstable1 A stable molecule with single bond2 A stable molecule with double bond3 A stable molecule with triple bond

Fractional bond order indicates paramagnetic nature of molecule.

Dipole Moment: Is defined as the product of the magnitude of charge (q) on the atom and the distance between the atom (d).

 = q x d

Its unit is debye (D)

1D = 10-18 esu-cm

e.g., CO2, CS2, CH4, BF3, XeF4

Polar molecule have non-zero dipole moment

e.g., NH3, PCl3, H2O, SF4, XeF6

Resultant Dipole Moment

Periodic Table and PeriodicityThere are 7 periods (Horizontal rows) and 18 groups (vertical columns)

Periodic Table and Periodicity History1. Doebereiner discovered group of three elements having similar properties and called them triads. The

atomic mass of the central element was the arithmetic mean of the atomic mass of other two elements e.g., Li, Na, K

2. Newlands law of Octaves: He arranged elements in their increasing atomic weights of the elements and properties of first element was found to be similar to that of eighth element.

3. Lother Meyer plotted graph between atomic volumes and atomic weight of the elements. Elements with similar properties had the similar position on the curve.

4. Mendeleev stated that "Physical and chemical properties of elements are periodic function of their atomic weight". Only 57 elements were known at that time.

5. Modern periodic Law: Moseley stated that physical and chemical properties of elements are periodic function of their atomic number.

6. Bohr given long form of periodic table.

Long Form of Periodic TableThere are 7 periods (Horizontal rows) and 18 groups (vertical columns)

1st period : Very short period (only two elements H11 and He4

2)2nd period : Short period (8 elements 3Li - 10Ne)3rd period : Short period (8 elements 11Na - 18Ar)4th period : Long period (18 elements 19K - 36Kr)5th period : Long period (18 elements 37Rb - 54Xe)6th period : Longest period (32 elements 55Cs - 86Rn)7th period : Incomplete period (26 elements 87Fr - 112Uub)

In the long form of periodic table elements can also be classified as:

a. s-Block Elements: Elements of group 1 and 2 having general electronic configuration ns1-2

ns1 - Alkali metal (Li to Cs)Fr is radioactivens2 - Alkaline earth metal (Be to Ba)

b. p-Block Elements: Elements of group 13, 14, 15, 16, 17 and 18 having electronic configuration ns2  np1-6. Elements of group 18 are also called as inert gases.

c. d-Block Elements: Also called as transition element having electronic configuration (n-1)d1-10  ns1-

2 (except 46Pd)

d. f-Block Elements: Also called as inner transition element, having electronic configuration (n-2) f1-14  (n-1) d0-

1  ns2. It includes 4f or lanthanoid (Ce to Lu) 5f or actinoid (Th to Lr)The elements are broadly divided into three types

i. Metals comprise more than 78% of the known elements.ii. Non-metals are less than twenty (C, N, P, O, S, Se, H, F, Cl, Br, l, He, Ne, Ar, Kr, Ar, Kr, Xe and Rn)iii. Elements which lie in the border line between metals and non metals are called metalloids. (B, Si, Ge, As,

Sb, Te, Po, At)Periodicity is observed in a number of properties which are directly or indirectly or linked with electronic configuration.

Effective nuclear charge increase across each period and remain almost constant down the group.

Zeff = Z - 

where 'Z' is nuclear charge is shielding effect

Atomic radii (is generally taken as covalent radii)

n = Principal quantum number of outer orbit

It generally decreasing across a period and increases down the group.

It is of three typesi. Covalent radiusii. Metallic radiusiii. van der Waal radius

Order: van der waal's radius > Metallic radius > Covalent radius

Ionic Radii

Cationic radii is smaller than anionic radii for some atom.

Cationic radii < Atomic < anionic radii

Elements of 2nd and 3rd transition series belonging to same group are similar in size and properties due to lanthanide contraction.

Ionisation Enthalpy is the energy required to remove the most loosely held electron from the gaseous isolated atom

Ionisation enthalpy generally decreases down the group.

Successive I.E of an atom have higher values.

IE1 <  IE2 <  IE3 .......

Electron gain enthalpy is the enthalpy change taking place when an electron is added to an isolated gaseous atom of the element.

The Ist electron gain enthalpy of most of the elements is negative as the process is exothermic.

Electron gain enthalpy becomes more negative from left to right in a period and less negative from the top to bottom in a group.

Successive electron gain enthalpies are always positive.

Electro negativity is the tendency of an atom to attract the shared pair of electron towards itself in a molecule.1. Electro negativity increases across the period and decreases down the groups.

2. Metals have low electro negativity and non-metals have high electro negativities.

3.Application of Electro negativity1. Percentage ionicity = 16 (XA ~ XB) + 3.5 (XA ~ XB)2

2. For oxides Xo ~ X element higher the difference more basic the oxide

Classifications of Organic Reactions - Organic ChemistryOn the basis of the products of the reactions; organic reactions are classified as...Classifications of Organic ReactionsOrganic Reactions have been broadly classified into two types on the basis of bond cleavage,

i. free radical reaction (hemolytic cleavage)ii. ionic reactions (heterolysis cleavage)

On the basis of the products of the reactions; organic reactions are classified as,

a. Addition Reactions

b. Substitution Reactions

c. Elimination Reactions

d. Rearrangement

Addition Reactions - Organic ChemistryA reaction in which the substrate and the reagent add up to form a product...

Addition ReactionsA reaction in which the substrate and the reagent add up to form a product is called addition reaction.

Compounds having multiple bonds such as, etc. undergo addition reactions.

I. Electrophilic Addition Reaction: This is a characteristic reaction of unsaturated hydrocarbons,

On bromination trans-2- butene gives meso-dibromide and cis-2- butene gives recemic (dl) modification. Thus, addition of Br2to the  -bond is the trans (or anti) addition. The reaction is, therefore, stereoselective.

The relative rates of addition of some substituted alkenes are as;

Electron withdrawing groups will have reverse effect.

Markownikov Rule: In case of addition of unsymmetrical reagents (i.e., HX) to unsymmetrical alkenes, the negative part of the addendum is added to that doubly bonded carbon which is less hydrogenated.

In the presence of organic peroxide or under conditions of radical formation, anti-Markonikov addition results. The peroxide converts into a free radical which generates a bromine-free radical from HBr.

Free radical addition of HF, Hl or HCl is energetically not favorable.

Addition of Br2 to Conjugated dienes

The 1,2 product predominates at lower temperature and 1,4-product predominates at higher temperature.

This may be due to stabilization of 1, 4-product by hyper conjugation. 

II. Addition to Alkynes:Alkenes are less reactive than alkenes because the  -electrons are more tightly held by the carbons. Electrophilic addition to alkynes resembles those of alkenes.

  

In the hydration of alkynes with sulphuric acid, the catalyst (such as mercuric salt) is necessary.

In case of aromatic compounds (e.g., benzene) addition reaction is energetically not favorable due to loss of resonance energy. 

III. Nucleophilic Addition Reaction:Electron-releasing groups conjugated to carbon-carbon multiple bonds favor electrophilic addition while electron withdrawing groups conjugated to carbon-carbon multiple bonds favor nucleophilic addition.

Polar functional groups, e.g.,  etc., also undergo nucleophilic addition.

Substitution Reactions - Organic ChemistryA reaction in which one group or atom is replaced by another...

Substitution ReactionsA reaction in which one group or atom is replaced by another is called a substitution reaction.

i. Free Radical Substitution: Alkenes undergo free radical substitution in the presence of light

CH4 + Cl2 CH3Cl + HCl

Light energy or heat causes homolytic fission of chlorine producing chlorine radicals which attack methane to methyl chloride.

When the ratio of CH4 to Cl2 is high, CH3Cl is formed predominantly and when Cl2 is in excess, all the hydrogens are replaced to give CCl4.

Ratio of rate of substitution. 

1 H 2 H 3 HIn Cl2 : 1 : 3.8 : 5In Br2 : 1 : 82 : 1600

ii. The number of types of H present in an alkane is equal to the number of monohalogen substituted products obtained by the halogenation of that alkane.

For example, Isopentane has 4 types of H, hence, isopenthane on chlorination will give four alkyl chlorides.

iii. Nucleophilic Substitution: The reaction which involves displacement of a nucleophile by another nucleophile is called nucleophilic substitution (SN) reaction. For example, hydrolysis of alkyl halide.

iv. Electrophilic (aromatic) Substitution: Due to having negative  -electron cloud, benzene ring discourages the nucleophilic attack and encourages electrophilic attack.

The typical reactions of benzene and its derivatives are electrophilic substitution.

Tautomerism - Organic ChemistryA very common form of tautomerism is that between a carbonyl compound...

TautomerismA very common form of tautomerism is that between a carbonyl compound containing an  -H and its enol form.

In simple cases, the equilibrium lies well to the left. In certain cases, however, a larger amount of the enol form is present. There are three main types of the more stable enols:

i. Molecules in which the enolic double bond is on conjugation with another double bond. For example, carboxylic esters have a much smaller enolic content than ketons. In molecules like acetoacetic ester, the enol is also stabilized by intramolecular hydrogen bonding.

ii. Molecules that contain two or three bulky aryl groups. For example, in case of 2, 2-dimesitylethenol, the keto content at equilibrium is only 5%. In this case steric hindrance destabilizes the keto form.

iii. Highly Fluorinated enols: The extent of enolization is greatly affected by solvant, concentratiom and temperature. Thus, acetoacetic ester has an enol content of 0.4% in water and 19.8% in toluene. In this case, water reduces the enol content by hydrogen bonding with the carbonyl, making this group less available for intramolecular bonding.

Other Proton-Shift Tautomerism1. Phenol-keto Tautomerism

For most simple phenols, the equilibrium lies well to the side of the phenol, since only on that side is there aromaticity.

2. Nitroso-Oxime Tautomerism

This equilibrium lies far to the right, and as a rule nitroso compounds arestable only when there is no  -hydrogen.

3. Nitro-acinitro Tautomerism

Primary and secondary nitroalkanes containing  -H undergo tautomerism.

4. Imine-enamine Tautomerism

Enamines are normally stable only when there is no hydrogen on the nitrogen (such as R2C  =  CR     NR2). Otherwise, the imine from predominates.

Factors Influencing Reactivity1. Inductive Effect

The electron pair forming the  -bond is slightly displaced towards the more electronegative atom. This permanent state of polarization is called the inductive effect.

 l effect (i.e., electron-withdrawing effect) : NO2 > F > COOH > Cl > Br > l > OH > OR > C6H5

+ l effect (electron-releasing effect) : Me3C - > Me2CH - > MeCH2 - > CH3

2. Electromeric EffectOn the close approach of a reagent, the electronic system of an unsaturated molecule is deformed. When the reagent is removed, the electronic system reverts to the original state. This kind of polarizability of multiple bonds is known as electronic effect.

Electromeric effect is temporary

3. Mesomeric EffectThe permanent polarization of a group conjugated with a  -bond or a set of alternate  -bonds is transmitted through the  -electrons of the system resulting in a different distribution of electrons in the unsaturated chain. This is called mesomeric effect.

+ M effect possessing groups are : 

 M effect possessing groups are :  

4. HyperconjugationThe ability of the  -bond electrons of an  -C   H bond to undergo conjugation with the adjacent  -electrons is called hyperconjugation.

The ortho-and para-directing effect of methyl group in toluene is attributed to electron release by hyperconjugation.

Elimination Reactions - Organic ChemistryWhen two groups or atoms from adjacent carbons are eliminated...

Elimination ReactionsWhen two groups or atoms from adjacent carbons are eliminated with the formation of unsaturated compounds (alkene or alkyne), the reaction is called elimination reaction.

Huckel's rule: Huckel's rule based on molecular orbital calculations, predicts that electron rings will constitute an aromatic system only if the number of electrons in the ring is of the form, (4n + 2)   electron system, where n is zero or any positive integer. The rule predicts that rings of 2, 6, 10, 14 etc., electrons will be aromatic, while rings of 4, 8, 12, etc., will not be aromatic, while rings of 4, 8, 12, etc., will not be.

Antiaromaticity: Electron rings will constitute an antiaromatic system, if the number of electrons in the ring is of the form, 4n  electron system, where n is any positive number.

For aromaticity and antiaromaticity, the molecule must be planar.

e.g., is an antiaromatic compound.

Cyclooctatetraene is not planar but tub-shaped. Hence, it is neither aromatic nor antiaromatic. The reason for the lack of planarity is that a regular octagon has angles of 135 .

Stereoisomerism - Organic ChemistryStereoisomerismIt is due to the difference in arrangement of atoms or group in space.

It is classified into two types1. Configurational Isomerism2. Conformational IsomerismConfigurational Isomerism is further classified into (I) Geometrical Isomerism (II) Optical Isomerism.1. Geometrical Isomerism

In this, the isomer have different spatial arrangement of atoms or group around the double bonded carbon atom.

Necessary Conditioni. Carbon-carbon rotation must be restricted either double bond or by cyclic structure.ii. The group attached to doubled bonded carbon atom must be different.iii. Triple bonded carbon does not have stereogenic centre so it does not exhibit Geometrical isomerism.

The isomers which have similar group on the same side of the doubly bonded carbon are called 'cis' isomers and the isomers which have similar group on the opposite sides are called 'trans' isomers.

iv. In aldoxime and ketoxime the prefix 'syn' and 'anti' indicates 'cis' and 'trans' isomer respectively.v. If four different groups are attached to carbon atom then 'E' and 'Z' system is used if higher groups are

on same side then 'Z' system is used and if higher groups are on opposite side then 'E' system is used.vi. Geometrical isomer shows different physical properties. There chemical properties are similar but not

identical.vii. Cis-isomer is more polar and have higher boiling point that trans-isomer.viii. Trans-isomer are more stable and have higher melting point then cis-isomer.

2. Optical IsomerismThese isomers resembles in their chemical properties but shows different behavior towards plane polarized light.

Necessary Conditioni. Organic molecules must have chiral centre when all the group bonded to carbon are different then the

carbon is called as chiral carbon or assymetric carbon.ii. Organic molecules must show enantiomerism i.e. non-super imposable mirror images. For this,

molecules must have chiral centre and must not have plane symmetry.

Optical isomer may be dextrorotatory or laevo rotatory depending upon the rotation of plane polarized light.

Representation of the structure (Fischer Projection)iii. Most oxidised carbon is arranged vertically at the top.iv. Group attached to carbon atom are assigned a priority which is divided on the basis of atomic number.v. Rotate the molecule such that the group of lowest priority is directed away. If rotation is clockwise the

configuration is 'R' and if the rotation is anticlockwise then configuration is specified as 'S'.

vi. If group of lowest priority is at the top of vertical line then rotate the molecule through180  to bring atom of lowest priority at the bottom.

vii. If group of lowest priority is on the lefts hand side, then position of atoms are group are changed in anticlockwise direction to bring the group of lowest priority at the bottom except changing the position of the group present at the top and vice versa, if the group of lowest priority is present on the right hand side.

Properties of Enantiomersviii. They have almost identical physical properties.ix. They rotate the plane polarized light in opposite direction to same extent.x. They have identical chemical properties.

Diastereomer: Stereomers which are not the mirror image of each other are called as diastereomers.They have different physical properties, they may or may not be optically active.

Meso Compounds: These compounds are optically  inactive inspite of the presence of chiral carbon atoms .This is due to presence of plane symmetry.

Racemic mixture: It is equimolar mixture of (+) and (-) enantiomers. This mixture is optically inactive due to external compensation.

Resolution: It is the mtehod of separation of Racemic mixture. The mixture is treated with a suitable optically active reagent which give a mixture of two diastereomers which are separated by fractional crystallization.

Number of possible Stereoisomers in a compound.xi. If molecule can not be divided into two equal halves

No. of 'd' and 'l' form = 2n

No. of meso form = 0Where 'n' is number of assymetric carbon.

xii. When molecule can be divided into equal halvesn = evenNo. of d and l form = 2(n-1)

No. of meso form = 

xiii. If n = odd

No. of 'd' and 'l' form = 2n-1  -  

No. of meso form = Conformational IsomerismIt arises due to the rotation through single bond. This results in staggered and eclipsed structures. e.g., ethane

All other conformation between eclipsed and staggered form may be obtained by rotating the two adjacent carbon to 60 C. Staggered > Gauche > Partially eclipsed > Fully eclipsed.