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### Vapour density of mixture of NO2 and N2O4 is 34.4 , then percentage abundance (by volume) of NO2 in mixture is .

Molecular weight = 2×VD
= 2× 34.5 = 69 u
Consider ℅ of NO2 is "x" then % of N2O4 is "100-x"

### What are the structure of CO2 , NO2+ , OCN- , SCN- ?

These molecules are isoelectronic so structure are also similar :

### Why does CO form a coordinate bond?

In carbon monoxide molecule carbon and oxygen form a double bond by sharing of two bond pairs , in which
carbon as well oxygen contributes 2 electrons to each other to form a double bond .
Now octet of oxygen is completed but carbon is left with two (2) valence electrons and it has a total of six electrons so it's octet is incompleted.

Hence carbon is relatively unstable than oxygen atom because oxygen has nearest noble gas configuration of 8 electrons in their valence shell.

So in order to attain stability oxygen contributes one of its lone pair of electrons to the carbon atom in the formation of a coordinate bond . This leads to completion of octet of both carbon and oxygen .
Important note:
In coordinate bond a pair of electrons is shared between two atoms but it is contributed by a single atom( Here contributor of lone pair is oxygen atom).

Similar Questions:

### How can draw the Lewis Structure of CO?

The electronic configuration of carbon and oxygen atoms as

C6 =1s2 2s2 2p2
O8 =1s2 2s2 2p4

This information can be used to determine the Lewis Dot Structure of  Carbon monoxide (CO):

Step 1: calculate total valence electrons  for carbon and oxygen atoms.

C = 4
O = 6

Total electrons in CO molecule =10

Step 2: Find octet electrons for each atom , carbon and oxygen

C: 8
O: 8

Total octet electrons =16

Step 3: Find the bonding electrons Subtract total valence electron from total octet electrons

16-10=6 electron (3 bond pair)

Step 4: Find number of bonds between carbon and oxygen atoms  by dividing the number of bonding electrons by 2

6-electrons/2 = 3 bonds

Step 5: The rest are non bonding pairs. Subtract bonding electrons  from valence electrons .

10-6= 4e-= 2 lone pairs

The Lewis structure of CO is identical with that for HC:::CH  except that the C-H bond pair replace by lone pairs.

"CO is also isoctronic with CN-"

### How can describe the bonding in PF5 using hybrid orbital?

The electron-pair and molecular geometry oF PF5 are trigonal-bipyra- midal according to its Lewis structurc and VSEPR theory. Five covalent bonds must point to the corners of a trigonal bipyramid. Therefore, the P atom must  have a single electron in each of five hybrid orbitals. the hybrid scheme is  Sp3d is required.
Each of the five P-F sigma bond involves overlap of one of the phosphorus spec hybrid orbital with fluorine 2p orbital.

### What is Arrhenius equation ?

The temperature dependence of rate of a chemical reaction can be accurately explained by Arrhenius equation. It was first proposed by Dutch chemist   J.H. Vant’s Hoff but Swedish chemist Arrhenius provides its physical justification and interpretation.
Where
K= Rate constant
A= Arrhenius constant or frequency factor or pre exponential factor
R= Universal gas constant =25/3 joule per mole per second
Ea= Activation Energy
T= temperature
-Ea/RT= Boltzmann factor or fraction of molecule having equal or greater than Activation energy or fraction of molecule that have kinetic energy greater than activation energy.

### What is " Clasius Claperon" equation ?

The dependence of vapour pressure and temperature is given by CLASIUS CLAPERON equation.

Vapour pressure of a particular liquid system is only the function of temperature only. It is independent from all other

### What is "Anoxia" conditions ?

At high altitudes the partial pressure of oxygen is less than that at the ground level. This leads to low concentrations of oxygen in the blood and tissues of people living at high altitudes or climbers. Low blood oxygen causes climbers to become weak and unable to think clearly, symptoms of a condition known as anoxia.

### What is bends condition and what is relation of bends with Scuba divers ?

Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends, which are painful and dangerous to life.
To avoid bends, as well as, the toxic effects of high concentrations of nitrogen in the blood, the tanks used by scuba divers are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen).

### What is effect of temperature on vapour pressure ? Explain with CLASIUS CLAPERON equation.

Factors affecting vapour pressure:
(A) Temperature:.
(1) The temperature at which the vapour pressure of the liquid becomes equal to the atmospheric pressure is called its boiling point.
(2) Vapour pressure is directly proportional to theTemperature so that on increasing temperature the rate of evaporation increases and rate of condensation decreases and hence vapour pressure increases.
(3) The dependence of vapour pressure and temperature is given by CLASIUS CLAPERON equation.

(4) Vapour pressure of a particular liquid system is only the function of temperature only. It is independent from all other

### What is vapour pressure and What is effect of temperature on vapour pressure ?

VAPOUR PRESSURE:
(1) If a sample of water in its liquid phase is placed in an empty container, some of it will vaporize to form gaseous of water. This change is called evaporation.
(2) The pressure exerted by the vapour (molecules in the vapour phase) over the surface of the liquid at the equilibrium at given temperature is called the vapour pressure of the liquid.
OR
(3) It is the pressure exerted by the vapour when vapours are equilibrium with the liquid.
(4) The pressure exerted by vapours is called unsaturated vapour pressure or partial vapour at non equilibrium condition
Factors affecting vapour pressure:
(A) Temperature:.
(1) The temperature at which the vapour pressure of the liquid becomes equal to the atmospheric pressure is called its boiling point.
(2) Vapour pressure is directly proportional to theTemperature so that on increasing temperature the rate of evaporation increases and rate of condensation decreases and hence vapour pressure
increases.
(3) The dependence of vapour pressure and temperature is given by CLASIUS CLAPERON equation.

(4) Vapour pressure of a particular liquid system is only the function of temperature only. It is independent from all other factors like surface area, amount of liquid, available space etc.

### What are the Important structure information of Diamond?

Lattice of Diamond is ZnS type structure.
(1) C- form FCC (4-atom)
(2) C- atoms present at the
Alternative tetrahedral voids (4-atoms)
(3) Total Number of one lattice unit is eight(8) hence molecular formula of diamond is (C8)
(4) Number of C-C bond in lattice cell is = 4×4= 16
(5) Number of C-C bond per carbon atom is 16/8=2
(6) the distance between two Carbon atom is d_C-C = a√3/4
(7) PE = π√3/10= 0.34 or 34%
(8) Voids = 66 %

Only those atoms which form four covalent bond produce a repeated 3D structure using only covalent bonds i.g. diamond structure the latter is based  on of a face centred cubic lattice where four out of eight tetrahedral voids are occupied by canon atoms. Every atoms in this structure is surrounded tetrahedrally by four other. No discrete molecule can be dicemed in diamond .the entire crystal is giant molecule a unit cell of which is shown as below.

Germanium, silicon and grey tin also crystallize in the same way as diamond.

### Why are bridge head carbocations unstable?

According to Bredt's rule a bridgehead carbon atom of bicyclo compound cannot be sp2 hybridised or in other word a bridgehead carbon atom cannot be form double bond. unless the ring that contains at least eight atoms.

### How does leaching of aluminium ore take place by Serpeck's process?

Serpeck's Process: This process is applied to the bauxite ore containing Silica (White bauxite SiO2) as major impurity.
NOTE:Silicone Volatile at this temperature and removed easily.

### How does leaching of aluminium ore take place by Hall's process?

Hall's Process: This process is also applied to the bauxite ore containing ferric oxide (red bauxite Fe2O3) as major impurity. This process ore is fused with Na2CO3.

### How does leaching of aluminium ore take place by Baeyer' process?

Baeyer's Process: By Bayer's process commercially it is being carried out (for red bauxite) In other words this process is applied to the bauxite ore containing ferric oxide (red bauxite Fe2O3) as chief impurity. Ore roasted to convert ferrous oxide to ferric oxide.

### What are important ores of Aluminium ?

Important ores of Aluminium:
(1) Corundum (Al2O3)
(2) Diaspore (Al2O3.H2O)
(3) Bauxite (Al2O3.2H2O)
(4) Gibbsite (Al2O3.3H2O)
(5) Cryolite (AlF3.3NaF) or Na3AlF6
(4) Alunite (K2SO4.Al2(SO4)3.4Al(OH)3
(5) Spinel (MgOAl2O3)
(6) Felspar (K2O.Al2O3.6SiO3) or KAlSi3O8
(7) China Clay or Kaoline [Al2O3.2SiO2.2H2O]

### What are important ore of Iron ore ?

Important Ores of Iron:

 SN Ores Formula 1 Haematite (Red) Fe2O3 2 Magnetite Fe3O4 3 Siderite or Spathic FeCO3 4 Iron Pyrite (fool's Gold) FeS2 5 Goethite FeO(OH) 6 Limonite 2Fe3O4.3H2O Others Ores 7 Ilmenite  (FeO+TiO2) FeTiO3 8 Chromite (FeO+Cr2O3) FeCr2O4

### What is composition of Wrought Iron ?

Wrought iron:
Wrought is made by heating cast iron with haematite (Fe2O3) which oxidises C to CO, S to SO2 Si to SiO2, P, P4O10 and Mn to MnO . Where CO and SO2 escapes, manganese oxide (MnO) and Silica (SiO2combine to form slag.
Similarly phosphorus pentoxide combines with haematite to form ferric phosphate slag.

### What is composition of Grey Cast Iron ?

Grey Cast Iron: However when re molted pig iron is slowly cooled, Grey cast iron is results. In this form of cast iron carbon is found to be combined form of Graphite.

### What is composition of White cast iron ?

White Cast Iron: When re molted pig iron is suddenly cooled, white cast iron is results. In this form of cast iron carbon is found to be combined form as cementite (Fe3C).

### What are the composition of pig iron?.

Pig Iron: Composition:
 SN Impurities % 1 Carbon (C) 3- 4.3 2 Silicon (Si) 1-2.0 3 Manganese (Mn) 0.5-2.0 4 Phosphorous (P) 0.05-2.0 5 Sulphure (S) 0.05-1.0

### Why density of water is greater than ice ?

Ice and water both contains H2O molecules but in water H2O molecules are more compactly arrange than in ice.

Ice has a hexagonal cage like structure, inside it H2O molecules are not closely packed.hence there is more vacant space between the molecules of ice. As a result the volume increases due to the vacant spaces.  As a result density of ice decrease.
Other hand,On increasing temperature then kinetic energy of molecules increases as result the interaction between the molecules decrease and as a result the the molecules come closer to each other and the volume decreases, so the density increases.

The density of water is maximum at 3.98 ℃ approximately 4 degree celsius.

### Why ice floats on water at room temperature ?

At room temperature ice is less dense than liquid water, so it floats on water surface. The maximum density of water occurs around 3.98 ℃ or approx 4 degrees Celsius.

### What is synergic bonding ?

Carbon monoxide, CO, as a ligand binds itself to metal atoms through the carbon atom. It is a weak donor (a weak base). It forms a weak sigma-bond to the central atom. CO is also an acceptor ligand and from a π-bond to the metal. This characteristic property of back bonding stabilised the metal-ligand interaction.
For a better understanding of the nature of bonding in metal carbonyls, we have to consider first the molecular orbital energy level diagram of carbon monoxide given in the figure. 3-sigma, the highest occupied molecular orbital in CO is essentially a lobe projecting away from the carbon atom. When CO acts as a ligand. This orbital serves as a weak donor to the metal atom, and forms a bond as represented in Figure. The lowest unoccupied molecular orbltals of CO are the π* (2π) orbitals. These play an important part in bonding as they can overlap metal d orbltals having π symmetry. The resultant Interaction leads to the delocalisation of electrons from, filled d orbltals on the metal into the empty orbitals on the CO ligands.This in fact, is back bonding from metal to CO. The metal to ligand bonding creates a synergic effect which strengthens the bond between CO and the metal (Figure).
The MO energy level diagram for CO The filled 3-sigma and the vacant 2π-oribttols are important for bonding in the formation of metal carbonyls

### How to find number of isomers of a octahedral complex containing all different ligands for example ML2,L2,L3,L4,L5,L6 type ?

Let us consider a octahedral complexes [ML1L2L3L4L5L5]  where M is the central metal atom while L2, L2, L3 .... are six different ligands we  shall represent the ligands by smallcase letters a,b,c etc. and the metal by M. We can write 12"cis" isomers in which ligands are separated by at angle 90° and 3 "trans" isomers in which ligands are separated by 180°.

The geometrical isomers of Mabcdef areas follows.

M(L1)(L2)(L3) (L4)(L5)(L6):

"Cis" isomers: separated by 90°

(1,2)(1,3)(1,4)(1,5)

(2,3)(3,4)(4,5)(5,2)

(2,6)(3,6)(4,6)(5,6)

"Trans " isomers: separated by 180°

(1,6)(2,4)(3,5)

### What are necessary and sufficient conditions for coordination complex to show "optical isomerism"?

The necessary and sufficient condition to show optical isomerism is , the complex as the whole must be asymmetrical by the absence of element of symmetry , plane of symmetry (POS) and center of symmetry ( COS).

### What are condition for geometrical isomerism in coordination compounds?

Among all type of geometries in coordination compounds, only squar planer , octahedral and dodecahedral will show geometrical isomerism. The necessary and sufficient conditions is for every position of ligands there must be at least one "CIS" (separated by 90°) and one must be "TRANS" (seperated by 180°).

### What is the temperature at density of water is maximum ?

The maximum density of water is an exceptionally give a irregular trends, which reaches a density peak at 3.98 °C ~ 4.00℃ or (39.16 °F).

### Arrange the silicon halides into decreasing order of Lewis acids Character? SiF3, SiCl3, SiBr3, SiI3

In case of silicone halides inductive effect dominate over back bonding hence lewis acid character decided by inductive effect.
Hence order of lewis acid character   SiF>SiCl3 > SiBr> SiI3

### What is d-orbital resonance?

D-ORBITAL RESONANCE:
It is a phenomenon in which electrons of ms and np get delocalized to vacant nd orbital because this availability of vacant d orbital to expect back bond get reduced .
In those molecules species where d orbital’s resonance exist of back Bonding is decreased.

### What is conditions for back bonding ?

CONDITIONS FOR BACK BONDING:
(1) Both of the atoms bonded with back Bonding are must be present in 2nd-2nd or 2nd-3rd period.
(2) One of the atoms has lone pair and another have vacant Orbital and direction of back Bonding depends upon vacant Orbital.
(3) The donor atom must have localized donatable electron pair. In general these are later half second period P - block elements (F, O, N and C).(4) The acceptor atom must have low energy empty orbital which generally are np or nd orbitals. Small and similar sized orbital’s favour overlap.

### BCl3 ,BBr3 BI3 and B(Me)3 are electron deficient but do not undergo dimerization why ?

BCl3 ,BBr3 BI3 and B(Me)although  they are electron deficient compound but do not undergo dimerisation  because  of steric factor in demmeric formed.

### Why some compounds are undergoes dimerization ?

Compound are dimerized due to following reasons:
(1) If there is no steric crowding and back bonding in a molecules then bridge bond formed and molecules dimerised and stabilized and dimerisation are more stable than back bonding.
(2) Most of the electron deficient compound attains stability by performing back bonding or they undergo dimerisation provided certain conditions are fulfilled
(3) BCl3 ,BBr3 BI3 and B(Me)although  they are electron deficient compound but do not undergo dimerisation  because  of steric factor in demmeric formed

### How do you calculate the number of all possible structural isomers for alkanes?

Yes we can find all possible structural isomers Of a given hydrocarbon.

Number of total structural isomers = 2^(N-4)+1

Where N is number of carbons in hydrocarbon

Example: (1)
Number of structural somers of butane (C4H10) is

SOLUTION:

Where , n=4
=2^(4-4)+1
=2^(0)+1
=1+1
=2

Example: (2)
Number of structural somers of butane (C5H12) is.

SOLUTION:

Where , n=5
=2^(5-4)+1
=2^(1)+1
=2+1
=3

Example: (3)
Number of structural somers of butane (C6H14) is.

SOLUTION:

Where , n=6
=2^(6-4)+1
=2^(2)+1
=4+1
=5

Example: (4)
Number of structural somers of butane (C7H16) is.

SOLUTION:

Where , n=7
=2^(7-4)+1
=2^(3)+1
=8+1
=9

Example: (5)
Number of structural somers of butane (C8H18) is.

SOLUTION:

Where , n=8
=2^(8-4)+1
=2^(4)+1
=16+1
=17

Example: (5)
Number of structural somers of butane (C8H18) is.

SOLUTION:

Where , n=9
=2^(9-4)+1
=2^(5)+1
=32+1
=33

### How to find number of stereoisomers in a large compound (polyenes) containing double bonds?

Number of stereoisomer of polyenes can calculated by following formulas .

### What is denticity of NO and NO+ ligands ?

"NO" is a special ligand which can donate three electrons (3e) to the central metal atom in neutral state but in charge state (NO+) it can donate two electrons only to the central atoms.

### What is water in oil emulsions ? explain with examples.

Water in oil emulsions: In this type of emulsions, water acts as dispersed phase and oil (organic solvent) acts as dispersion medium. Cold cream, butter etc, are examples of oil emulsions.

### What are Oil in water emulsions ? explain with examples.

Oil in water emulsions: In this type of emulsions, oil acts as (organic solvent) dispersed phase and water acts as dispersion medium. Some examples of this type of emulsions are milk, vanishing cream, etc. In milk, liquid fat is dispersed in water.

### How many 3c-2e bonds and 3c-4e are there in Al2(CH3) 6?

Al2(CH3)6 is dimer of Al(CH3)3 , which is dimerized by formation of bridge bond namely 3C - 2e bond (banana bond ) as well as 3C - 4e bond .

### Why are all P-Cl bond lengths equal in PCl3 but different in PCl5?

Phosphorus atom of PCl3, is sp3 hybridised. so orbital involved in hybridization are s and p only and PCl3 has a trigonal pyramid structure.

However in case of PCl5, the hybridisation is sp3d. (sp3d, the hybridisation can represent as also sp2+pd) and it acquired TBP ( trigonal pyramidal structure).
We know that in TBP, there is two type of bond present I.e. axial (longitudinal) and equatorial bond. Bond length of axial bond is longer (coordinate bond ) while equatorial bond is shorter due to covalent nature ( formed by overlapping of atomic orbitals).

### Are all bonds of If7 equivalent ?. If Not then explain ?

In IF7 seven fluorine atoms are coordinate with iodine centre, whose coordination geometry is pentagonal bipyramidal.  And hybridization is Sp3d3 but at room temperature, this structure is conformationally mobile,

### What is "EMULSIONS"

Emulsions are colloids in which both dispersed phase and dispersion medium are liquids.
Emulsion can be broadly classified into two types.
(i) Oil in water emulsions: In this type of emulsions, oil acts as (organic solvent) dispersed phase and water acts as dispersion medium. Some examples of this type of emulsions are milk, vanishing cream, etc. In milk, liquid fat is dispersed in water.
(ii) Water in oil emulsions: In this type of emulsions, water acts as dispersed phase and oil (organic solvent) acts as dispersion medium. Cold cream, butter etc, are examples of oil emulsions.
Identification of Emulsion
The following tests may be employed to distinguish between the two types of emulsions:
(i) Dye test: Some oil soluble dye is added to the emulsion. If the background becomes coloured, the emulsion is water – in – oil type and if the coloured droplets are seen, the emulsion is oil – in – water type.
(ii) Dilution test: If the emulsion can be diluted with water, this indicates that water is the dispersion medium and the emulsion is of oil – in – water type. In case the added water forms a separate layer, the emulsion is water – in – oil type.
Preparation of Emulsion:
The process of making an emulsion is known as emulsification. Emulsion may be obtained by vigorously mixing both the liquids. The dispersed drops at once come together and form separate layers. To stabilize an emulsion, the addition of a small quantity of a third substance known as emulsifying agent or emulsifier is essential. Soaps and detergents are most frequently used as
emulsifiers.
The other common stabilizing agents are proteins, gum and agar-agar.

### What is application of colloids ?

Colloids including emulsions find a number of uses in our daily life and industry. Some of the uses are given below:
(i) Rubber plating: Latex is a colloidal solution of negatively charged rubber particles. Rubber plated articles are prepared by depositing negative charged particles over the article to be rubber plated by making that article an anode in a rubber plating bath.
(ii) Medicines: Medicines in colloidal form are easily absorbed by the body tissues and hence are more effective.
(iii) Sewage disposal: Colloidal particles of dirt, mud etc. carry electric charge. Hence when sewage water is passed through the plates kept at a high potential, the colloidal particles are
coagulated due to electrophoresis and the suspended matter gets removed.
(iv) Purification of water: The precipitation of colloidal impurities present in water can be done by adding certain electrolytes like alum etc. The negatively charged colloidal particles of
impurities get neutralized by the Al3+ ions and settle down and pure water can be decanted off.
(v) Formation of delta: River water contains charged colloidal particles of clay, sand and many other materials. Sea water is a very big store – house of a variety of electrolytes dissolved in it. As soon as river water comes in contact with sea water, the electrolytes present in sea water coagulate the suspended colloidal particles which ultimately settle down at the point of contact and thus the level of the river bed rises. As a result, water adopts a different course and delta is formed in due course of time.
(vi) Smoke screen: In warfare, smoke screens are used which are colloidal dispersion of certain
substance in the air.

### What is "peptization" ?

Peptization may be defined as the process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte. The electrolyte used for this purpose is called peptizing agent. This method is applied, generally, to convert a freshly prepared precipitate into a colloidal sol.
For example, when freshly precipitated Fe(OH)3 is shaken with aqueous solution of FeCl3(peptizing agent) it adsorbs Fe+3 ions and thereby breaks up into small – sized particles.

### Why medicines are more effective in colloidal state?

A colloidal state has larger surface area of sol particles and this shows more effective adsorption. Thus medicines in colloidal state are more effectively absorbed and give better results.

### What is Associated Colloids (Micelles) ?

There are some substances which at low concentrations behaves as normal, strong electrolytes but at higher concentrations exhibit colloidal  behaviour due to the formation of aggregated particles. The aggregated particles thus formed are called micelles. These are also known as associated colloids.
The formation of micelles take place only above a particular temperature called kraft temperature (Tk) and above a particular concentration called critical micelle concentration (CMC). On dilution, these colloids revert back to individual ions. Surface active agents such as soaps and synthetic detergents belong to this class. For soaps, the CMC is -10-4
to 10-3 molperL.
These colloids have both lyophobic and lyophilic parts. Micelles may contains as many as 100 molecules or more.

### Acetyl chloride on reduction with H2 in presence of Pd as catalyst gives ethanol, whereas in presence of Pd-BaSO4, it gives ethanal.

Solutions are homogenous systems e.g. sugar solution. If sand is stirred in water, it slowly settles down and is called a suspension. Between the extremes of suspensions and solutions a large group of systems called colloidal dispersion or simply colloids exist.
A colloidal is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium. The essential difference between a solution and a colloidal is one of particle size. In a solution, the particles or ions are small molecules. In a colloid, the dispersed phase may consist a particles of a simple macromolecule (such as protein or synthetic polymer) or an aggregate of many atoms, ions or molecules. Colloidal particles are larger than simple molecules but small enough to remain suspended. They have a range of a diameter between 1 and 1000 nm.

### Comment on the statement that “colloid is not a substance but a state of substance”.

Any substance (solid, liquid or gas) using special method can be brought into colloidal state. For example, NaCl in water forms true solution but in benzene forms colloidal solutions in alcohol but colloidal in water.

### What is the relation between Total energy (TE), Kinetic energy (KE) and Potential energy (PE) of Bohr's orbits?

Relation between Total energy (TE), Kinetic energy (KE) and Potential energy (PE):

Important conclusions:
(1) The minus sign for the energy of an electron in an orbit represents attraction between the +vely charged nucleus and negatively charged electron.
(2) Energy of an electron at infinite distance from the nucleus is zero.
(3) As an electron approaches the nucleus, the electrical attraction increases, energy of electron decreases and it becomes negative.
(4) Energy of an electron increases as the value of ‘n’increases i.e.
(5) Value of ‘n’ remaining unchanged, the amount of energy associated with an electron remains unaltered.
(6) Energy of electron in firstsecondthird and fourthorbit are –13.6, –3.4, –1.5, and –0.85 eV/atomrespectively.
(7) Although the energy of electron increases with increase in the value of ‘n’ (orbit), yet the difference of energy between successive orbits decreases. Thus E2 – E1 > E3 – E2 > E4 – E3 > E5 – E4 >, etc…

### How to calculate energy of Bohr's orbits in term of Rydberg's constant

Energy in term of Rydberg’s Constant:

### Which of the Hydrogen spectrum series found in visible range of spectrum?

Balmer series of Hydrogen spectrum found in visible range of spectrum while lymen series found in UV range of spectrum and remain series of spectrum found in Infra red of spectrum..
More over only first four line of Balmer series found in visible range and others line of Balmer series Lines  also found infrared part of spectrum.

### Of all noble metals, gold has got a relatively high electron affinity. Explain.

The increased effective nuclear charge due to poor screening by inner 4f and 5 d orbitals enhances the attracting ability and hence it has got high electron affinity.

### Li2CO3 decomposes on heating but other alkali metal carbonates don’t. Explain.

Packing in crystal lattice is not compact due to small size of Li+ and bigger size of CO3 -2 .But O2– being smaller in size can stabilize Li2O.

### The electronegativities of B, Al, Ga are 2.0, 1.5, 1.6 respectively. The trend is not regular. Explain.

As we go down the period the electronegativity decreases. But after Al, due to the presence of d electrons which have minimum shielding effect, the nuclear charge increases and hence electronegativity also increases.

### The first ionization energy of carbon atom is greater than that of boron atom, whereas reverse is true for the second ionization energy. Explain.

The electronic configuration of carbon and boron are as follows:
C: 1S2 ,2s2 2px1,2py1
B: 2S2 , 2s2,  2px1
Due to higher nuclear charge in carbon, the force of attraction towards valency electron is more in carbon atom and hence the first ionization energy is greater than boron atom. After loss of one electron, the mono-valent cations have the configurations as follows:
C: 1S2 ,2s2 2px1,
B: 2S2 , 2s2,
configuration of B+ is stable one and hence the removal of electron is difficult in comparison to C+.Hence, second ionization potential of boron is higher than carbon.

### The electron affinity of sulphur is greater than oxygen. Why?

This is because of smaller size of oxygen due to which it has got higher charge density and thus electronic repulsion increases as it takes electron. So its E.A. is less than sulphur.

### In alkali metal group which is the strongest reducing agent in aqueous solution and why?

Lithium (Li) is the strongest reducing agent. Since I.P. decreases down the group we would expect that Li will have the lowest reducing power in that group. But since its hydration energy is very high and which in fact decreases down the group, Li will have highest reducing
power.

### Why there are 2, 8 and 8 elements in first, second and third periodic of periods table respectively ? Explain.

In first period 1s is completed. Its capacity is of two electrons. In second period 2s 2p and in third period 3s 3p are completed. The capacity of these shells is of 8 electrons each. Thus, 2, 8 and 8 elements are present in first, second and third periods respectively.

### What is atomic volume ? and what is periodicity of atomic volume in groups and periods ?

ATOMIC VOLUME:
Atomic Volume of is define as the volume occupied by one mole of atoms or gram atom of the given element in the solid state .
Thus Atomic volume = atomic weight in gram/ Density in solid state
(A) In general atomic volume generally leads to higher density as vice versa higher atomic volume generally leads to lower density.
(B) Trends in group:
When we move from top to bottom in a group the atomic volume generally increases.
(C) Trends in period:
When we move from move left to right along a period the atomic volume first decrease to minimum at mid period then increases.

### What is atomic density ? give the periodicity of atomic density in periods and groups.

ATOMIC DENSITY:
Density is the ratio of mass and volume. Higher the atomic volume leads to lower density as vice versa lower the atomic volume leads to higher density .
(A) Trends in group:
When we move top to bottom in a group the atomic density generally increases , it is due to increasing in atomic volume and atomic mass because too to bottom in group , number of shells increases but mass is more and more increases with respect to volume, so finally the atomic density ina group increases.
(B) Trends in period:
When we move from left to right along with a period , the atomic density increases and become maximum at mid period , and after that decrease.
(C) Atomic density depends upon two factors these are given as.
(i) the electronic configuration of inner most shells
(ii) packing capacity
EXCEPTION:
(1) Density of Na > Density of K
Reason:
The density of 'Na' is greater than the density of of 'K' .It is due to the inner shells of 'Na' atom is fully filled but the shells the inner most shells of 'K' not full filled.
11Na= 1s2 2s2 2p6 3s1 (Completely filled Inner shell s)
19K= 1s2 2s2 2p6 3s1 3p6 3d0, 4s1 (incomplete inner shells)
(2) Density of Mg > Density of Ca
Reason:
The density of 'Mg' is greater than the density of of 'Ca' .It is due to the inner shells of 'Mg' atom is fully filled but the shells the inner most shells of 'Ca' not full filled.
12Mg= 1s2 2s2 2p6 3s2(Completely filled Inner shell s)
20Ca= 1s2 2s2 2p6 3s1 3p6 3d0, 4s2 (incomplete inner shells)

### What is Mendeleev's periodic table ? give important features and draw back of Mendeleev's table.

Mendeleev’s Periodic Law:
Mendeleev, a Russian Chemist used broader range to physical and chemical properties to classify the elements. The physical and chemical properties of elements are periodic functions of their atomic weights. If the elements are arranged in the order of their increasing
atomic weights, after a regular interval elements with similar properties are repeated (inert gases were not discovered till then)
MENDELEEV'S PERIODIC TABLE:
Mendeleev arranged the discovered 63 elements in the periodic table into 7 horizontal rows known as periods and 8 vertical columns known as groups numbered 1 to 8.
Mendeleev Suggested:
(1) He excluded certain elements and assigned them a separate independent position.
(2) Leaving gaps for the then undiscovered elements
(3) When the properties of elements did not correspond to what is expected of the group they were named by prefixing Eka to the preceding element e.g. Eka boron (Silicon); Eka silicon (Germanium), Eka aluminum (Gallium); Eka Maganese (Technitium)
Uses of Mendeleev’s Periodic Table:
(1) Systematic study of the elements
(2) Atomic weights of elements were determined with the help of periodic table. Atomic weight = Valency × Equivalent weight = Group number × Equivalent weight.
(3) Atomic weight of elements were corrected. Atomic weight of Be was calculated to be 3 × 4.5 = 13.5 by considering its valency 3. Mendeleev calculated it 2 × 4.5 = 9.
(4) Discovery of new elements – In Mendeleev's periodic table two consecutive members differs by two or three units in the atomic weight. Where this gap was more, the gaps were left in the periodic table.
Defects of Mendeleev's Periodic Table:
(1) Position of hydrogen is uncertain. It has been placed in IA and VIIA groups because of its resemblance with both the groups.
(2) No separate positions are given to isotopes.
(3) It is not clear to which group lanthanides and actinides belong to.
(4) Although there is no resemblance except valency of subgroups A and B, they have been put in the same group.
(5) Order of increasing atomic weights is not strictly followed in the arrangement of elements in the periodic table. For e.g. – Co (At.wt. 58.9) is placed before Ni (58.7) and Ar (39.9) is placed before K (39)

### PERIODICITY IN PROPERTIES

TOPIC COVER:
[I]PERIODIC IN PHYSICAL PROPERTIES:
(1) ATOMIC DENSITY:
(2) ATOMIC VOLUME:
(3) MELTING AND BOILING POINT:
(4) VALENCY:
(5) SCREENING OR SHIELDING EFFECT:
(7) IONISATION POTENTIAL(IP)/ ENTHALPY:
(8) ECTRONEGATIVITY:
[II] PERIODICITY IN CHEMICAL PROPERTIES:
[III] PERIODICITY IN CHEMICAL REACTIVITY:

PERIODICITY IN PROPERTIES:
When elements are arranged in the increasing of atomic number , elements having similar properties recur at regular intervals in the periodic table . This type of property is called Periodicity.

CAUSE OF PERIODICITY:
(1) The cause of Periodicity in properties is due to the same outermist electronic coming at regular time intervals.
(2) In the periodic table, elements with similar properties recure at intervals of 2, 8, 8, 18, 18, 32, and 32, these numbers are called as magic numbers.
[I]PERIODIC IN PHYSICAL PROPERTIES:
(1) ATOMIC DENSITY:
Density is the ratio of mass and volume. Higher the atomic volume leads to lower density as vice versa lower the atomic volume leads to higher density .
(A) Trends in group:
When we move top to bottom in a group the atomic density generally increases , it is due to increasing in atomic volume and atomic mass because too to bottom in group , number of shells increases but mass is more and more increases with respect to volume, so finally the atomic density ina group increases.
(B) Trends in period:
When we move from left to right along with a period , the atomic density increases and become maximum at mid period , and after that decrease.
(C) Atomic density depends upon two factors these are given as.
(i) the electronic configuration of inner most shells
(ii) packing capacity
EXCEPTION:
(1) Density of Na > Density of K
Reason:
The density of 'Na' is greater than the density of of 'K' .It is due to the inner shells of 'Na' atom is fully filled but the shells the inner most shells of 'K' not full filled.
11Na= 1s2 2s2 2p6 3s1 (Completely filled Inner shell s)
19K= 1s2 2s2 2p6 3s1 3p6 3d0, 4s1 (incomplete inner shells)
(2) Density of Mg > Density of Ca
Reason:
The density of 'Mg' is greater than the density of of 'Ca' .It is due to the inner shells of 'Mg' atom is fully filled but the shells the inner most shells of 'Ca' not full filled.
12Mg= 1s2 2s2 2p6 3s2 (Completely filled Inner shell s)
20Ca= 1s2 2s2 2p6 3s1 3p6 3d0, 4s2 (incomplete inner shells)

(2) ATOMIC VOLUME:
Atomic Volume of is define as the volume occupied by one mole of atoms or gram atom of the given element in the solid state .
Thus Atomic volume = atomic weight in gram/ Density in solid state
(A) In general atomic volume generally leads to higher density as vice versa higher atomic volume generally leads to lower density.
(B) Trends in group:
When we move from top to bottom in a group the atomic volume generally increases.
(C) Trends in period:
When we move from move left to right along a period the atomic volume first decrease to minimum at mid period then increases.

(3) MELTING AND BOILING POINT:
(A) Melting point: The temperature at which  a solid material changes into the liquid material is called melting point and process is called melting.
(B) Boiling point the temperature at a liquid material changes into its vapour is called boiling point and the process is called boiling.
(C) Lower atomic volume generally leads to higher density , increases hardness and brittleness, less malleability and ductility.
(D) Trends in groups:
1- When we move top to bottom in group of S-Block, the melting point and boiling point decrease.
2- When we move top to bottom in all group of d-Block, the melting point and boiling point increases.
3- While we move IIIA TO VIA Groups , the MP and BP decreases.
4- While we move VA TO VIIA Groups , the MP and BP increases.
(E) Trends in period:
When we move from left to right through periodic table the value of MP and BP first increases to maximum after decrease like density.
(4) VALECNCY:
(5) SCREANING OR SHIELDING EFFECT:
(6.3) Vander waal's radius:It is define as half of the distance between nuclei of the two adjacent atom bonded with Vander waal's forces.
(1) The Vander waal's radius defined the atomic radius of inert gases.
(2) Vander waal's redius is greater than that of all known radius.
(4) Vander waal's force is directly proportional to the molecular weight.
(6.4) Metallic radius:It is defined as half of the inter nuclear distance between the nucleus of two adjacent atoms in the metallic lattice . Metallic radius is greater than Covalent radius.
(1) Nuclear attraction:
(2) principle quantum number:
(3) Screaning effect:
(4) Multiplicity of bond
(5) % S Character:
(C) Periodicity of atomic radius :
(1) In Group :when we move from top to bottom in group generally atomic radius increases as atomic number increases.this due to the addition of new energy shells increases, which overcome the effect of increased nuclear charge as results atomic radius gradually increase down the group.
(2) In Period : (A) When we move from left to right in group generally atomic radius decreases regularly in the representative elements because the principal quantum number remains same in period but the nuclear charge increases due to increased in nuclear charge the force of attraction towards nucleus increases, which brings contraction in size.
(B) In case of noble gas elements , the atomic radius increases exceptionally .It is due the fact that the noble gases have Vander waal's radius , which is always has higher value than Covalent radius.
(C) In case of transition elements , decrease in size is very less since the last or differentiating electrons of the elements into (n-1)d level . The additional electrons effectively screen much increased nuclear charge on the outer most  ns electrons therefore , size remains almost constant.

(7) IONIZATION POTENTIAL(IP)/ENTHALPY:
(A) Facter's affecting ionization enthalpy:
(2) Screening effect:
(3) Nuclear charge:
(4) Penentration effect of electrons:
(5) Half filled and fully filled configuration:
(B) Periodicity in ionization enthalpy:
(1) In group:
(2) In period :
(C) Application of Ionization enthalpy:
(1) Metallic and non metallic Character:
(2) Reactivity:
(3) Reducing Capacity:
(4) Oxidising Capacity:
(5) Type of bond :

(8) ENECTRON GAIN ENTHALPY/ENTHALPY:

(A) Facter's affecting EGE:
(2) Nuclear charge:
(3) Half filled and fully filled configuration:
(B) Periodicity in electron affinity:
(1) In Group:
(2) In period:
(9) ECTRONEGATIVITY:
(A) Facter's  affecting electronegativity:
(1) Nuclear attraction:
(3) Oxidation state:
(4) % S Character:
(B) Periodicity in electronegativity:
(1) In groups:
(2) In periods:
(3) Reason:
(C) Applications of electronegativity:
(1) Metallic and non metallic character:
(2) Bond energy (BE) :
(3) Bond lenght (BL):The nature of bond between two atoms can be decided on basis of electronegativity difference between bonded atoms
(a) The difference between electronegativity of two bonded ago is zero then , the bond is purely covalent.
(b) The % ionic Character in covalent bond can be calculated by the Henny Smith equation:
% Ionic Character=16 (Xa-Xb)+3.5(Xa-Xb)2
On the basis of this equation % ionic Character calculated as follows:
∆E=0
(4) Nature of Bond :
(5) Nature of hydrides:
(5) Nature of hydroxide:
(6) Nature of Oxides:
(D) Measurement of electronegativity:
(1) Mulliken Scale: According to Mulliken's the electronegativity of an atom is the arithmetic mean of first ionization enthalpy and it's electron gain enthalpy
(2) Pauling bond energy scale: this scale is based on the bond energies. According to Pauling, the the electronegativity difference XA-XB between two atom A and B is given by
XA-XB= 0.208[✓∆E]
Where ∆E =Resonance energy
∆E=Actual bond energy(EA-B) -✓EA2-EB2

ILLUSTRATIVE EXAMPLE: The ionic resonance of C-H bond is 5.75 kcal. The electronegativity of hydrogen is 2.1 . What will be the electronegativity of carbon?
ILLUSTRATIVE EXAMPLE : The value of ionic resonance energy of AB molecule is 4 kcal. The electronegativity of B is 2 . The electronegativity of A is :

(3) Relation between Mulliken and Pauling:
(4) Allred Roshow Scale:
(5) Relation between Allred Roshow and Pauling :

[II] PERIODICITY IN CHEMICAL PROPERTIES:

[III] PERIODICITY IN CHEMICAL REACTIVITY:

### What is Boyle's temperature ? and what is relation of Boyle's temperature with Vander waal's constant?

The temperature at which non ideal gas (real gas) exhibits almost ideal behaviour for a considerable range of pressure called Boyle's.
Boyle's temperature (TB) is related to Vander Waal’s constant as follows.
[TB = a / Rb]
Where (a) and (b)are Vander waal's constant represent  force of attraction and Volume correction respectively. And (R) is universal gas constant

The Gases which are easily liquefied have a high Boyle's temperature, for example
[TB (O2) = 406 K ]
Other hand the gases which are difficult to liquefy have a low Boyle's temperature, for example.
[TB(He) = 23 K]