CLASS IX, X , XI , XII , NEET and JEE
CLASS :- 11
Atomic number and modern periodic law
In 1913 moseley
young English physicist discovered the relationship between x-ray spectra and the atomic number of the element when high energy electron were focused on target made of the element(heavy metal) under study x-ray were generated ,
he founded that the frequency of X rays emitted from the element and observe the frequency of the the the prominent x-ray emitted by an element was proportional to the atomic number and not to the atomic weight
According to moseley
✔v = a(Z-b)
v= frequency , A and B = constant that are the same of all the element
a plot of ✔v versus atomic number Z give a straight line
this lead , that Atomic number and not atomic weight is the fundamental property of the element it therefore suggest that atomic number instead of atomic weight should be the basis of classification of the element the acceptance of atomic number as the important characteristic of an atom lead to the modern periodic law
The physical and chemical properties of the element are periodic functions of their atomic numbers.
Discovery and nomenclature of elements with atomic number more than 100
The discovery of the many new element after uranium these were called transuranium element today we have element up to 118 this element were early name traditional wear the discover our Discover
The discovery new element with very high atomic number are very unstable and only minute quantities are sometime only a few atom of this element are obtain their for scientist before collecting the reliable data on the new element at time try to obtain claim for it is described for example element 104 atomic number the Americans name it at the rutherfordium (Rf) while Soviet name it kurchatovium (Ku) the overcome to overcome this problem scientist propose a system of nomenclature Of element , nomenclature of inorganic chemistry CNIC and IUPAC in 1997 give the approval official name of the element with atomic number 104 to 109
The nomenclature of new element on the basis of Latin word for atomic number
example Nil for 0 and un for 1 , bi for 2 w, tri for 3
[as 104= un+nil+quad+ium=unnilquadium] and so on As given in table
And in last added ium
[as 106 = un + nil + hex + ium = unnilhexium]
The long form of the periodic table
the long form of the periodic table this is constructed on the basis of repeating electronic configuration of the atom when the element arrange in the order of increasing atomic number long form of the periodic table
structures feature of the long form of the periodic table
in the long form of the periodic table consists of the horizontal row called period
and vertical column called group
In the long form of periodic table total number of period 7 and group 18
Each period represent outermost cell of element means first period show that every element (H ,He) have first outer cell (1s)
second period means each element have second outermost shell(2s,2p) means the period number so that outermost cell of each element which located in their respected period
(1) first period means first energy level have only one atomic orbital(1s) and one atomic orbital only have 2 electrons(1s1 or 1s2) then in first period have only two element hydrogen and Helium
(2) in second period means in second outermost cell only have two sub energy level 2S and 2P then total number of 8 element are located in second period (atomic orbital 2s , 2px ,2py , 2pz)
(3) in third period means third outermost cell have three sub energy level 3s,3p and 3d
but 3d energy level more than 4s than third period have only to sub energy level 3S and 3p it means total number 8 element located in third orbital (atomic orbital 3s , 3px, 3py , 3pz)
(4) In the fourth period the total number of electrons is 18 because the 4th period has three subshells 4S 3d and 4p (atomic orbital 4s , 3dxy , 3dyz . 3dzx , 3dx2-y2 and 3dz2 , 4px , 4py, and 4pz)
(5) in 5th period have 18 electron because 5th period have three sub energy level 5S 4D and 5P
(atomic orbital 5s , 4dxy , 4dyz . 4dzx , 4dx2-y2 and 4dz2 , 5px , 5py, and 5pz)
(6) in sixth period total number of element 32 because in 6th period total number of sub energy level 6s, 4f 5d and 6p
(7) In seventh period have 4 subshell 7s 5f,6d and 7P then total number of element occupied in seventh period 32 but today it is incomplete
Classification of Element in different group
s-Block Elements
In the s-block elements, the last electron enters the S -Orbit. The maximum
capacity of first energy shell is of two electrons, thus, these elements have valence shell configuration of either ns1 or ns2.
The general electronic configuration of s block element nS1 TO nS2
General Characteristics of s-block Elements
1. S –block element have to group fist (alkali metal ) and second (alkaline
earth metal )
2. They are soft metals, possess low melting and boiling points,
3. They have the largest atomic radii in their corresponding periods
4. They are good conductors of heat and electricity.
5. They have low values of ionization energies
6. They are highly electropositive nature metal .
7. They are very reactive and readily form ionic compounds
8. They valency of first group element +1 (monovalent) while second group show +2 (bivalency).
9. They are never found in free state in nature due to their reactive nature.
10.they act as strong reducing agents.
11.The alkali and alkaline earth metals cannot be prepared by doing electrolysis of aqueous solutions of their salts.
12.The compounds of s-block elements are predominantly ionic and colourless. However, lithium and beryllium compounds are covalent in nature.
13.They have great affinity for oxygen and halogen (non metal).
14. the compound of s block element as an oxides are basic. The hydroxides are strong alkali.
15.They displace hydrogen from acids (HCl and H2SO4)and form corresponding salts.
P - Block Elements
The element in which the last electron enter the P-orbits of their outermost energy level are called P- block element the element of group 13 to 18 involving addition of 1 2 3 4 5 and 6 electron respectively in p orbital (p1to p6)and S orbital(s2) are are already fill in there atom constitutes P block
General Characteristics of p-block Elements(1) They include both metal and non metal there is regular change from metallic to non metallic character as we move along A period from left to right in this block the metallic character increase as we go down the group
2 Their ionization enthalpy are relatively higher as compared to S block element
3 They form mostly covalent compound 17 group is also form ionic compound
4 In this group some of them so more than one Oxidation state in their compound example chlorine so - 1 to + 7 oxidation number compound (HCl and Cl2O7)
5 The General electronic configuration ns2,np1 to ns2np6
6 We move from across the period of this p-block, oxidizing character increase
7 The element of s and p block are collectively called representative element the element of last group having ns2 and nP6 configuration are called noble gas all the orbital in the valency cell of the Nobel gases are completely filled and they have no tendency to loss or gain electron
8 in this group element the non metallic character increases as we move from left to right across a period and metallic character increases we go down in the group
group 13 to 18
d-Block Elements
The element in which the last electron enter the d orbitals of their last but one called penultimate energy level[ (n-1)d] constitute d- block element .
This block constitute of the element lying Between s and p block starting from 4 period and onwards in this block total 10 group , from group 3 to 12
The d orbital which is progressively being field in the element of this group this element are also called Transition Element because the properties of this element are Midway between those of S block and P block element in a way transition metal from a bridge element the chemical active metal of S block element and the less active element of group 13 and 14 therefore the represent transition at change in behavior and take their family name Transition Element .
Transition Element have free complete row of 10 element a transition series
(1) first transition series is scandium(z=21) to zinc(Z=30)
(2)second transition series yttrium (Z=39) to cadmium(Z=48) 4d series
(3) third transition series lanthanum (z=57) , hafnium (z=72) to Mercury(z=80) 5d series
(4) 4th transition series actinium (z=89) rutherfordium (z=104)to copernicium (z=112) 6d series
General Characteristics of d-block Elements1 the transition metal having high melting and boiling point
2 in the transition metals most of them form colour compound
3 They have a good tendency to form complex compound
4 Their compounds are generally paramagnetic they exhibit several Oxidation State most of the Transition Element such as Mn, Nickel platinum and their compound are used as a catalyst
5 They also form complex colourful iron and
6 The transition Element good conductor of heat and electricity
7General electonic configuration nS0 to nS2 and( n-1) d0 to( n-1) d10
F-Block Elements
The element in which the last electron enter the f orbital [(n-2)f] of their atom are called f- block element in these element the last electron is added to the third [(n-2)f]of the outermost energy level
F- block element have two series of element place at the bottom of the periodic table
(1) first series followed lanthanum and the element present in the series - cerium to lutetium are called lanthanoid a lanthanides these are also called a rare earth metal
(2) 2nd series follow actinium . and the element present in the series Thorium to Lawrence these are called actinoid or actinides these are of radioactive nature
the general electronic configuration of F block element may be written (n-2)f1 to (n-2)f14
element include in this two series are called in a Transition Element because they form transition series within the Transition Element of developed general characteristic of F block elements the general characteristic of a block element are first
General Characteristics of F-block Elements(1) They are heavy metal
(2) They generally have high melting and boiling point
(3) The exhibit variable Oxidation state in their respected ions are compound
(4) They form colour compound or ion
(5) They have the tendency to form complex compound
(6) actinoid are radioactive nature
(7) after uranium are called trans uranium element
Classification of element
1 Noble Gas :-
the noble gas are found at the end of each period in group 18 except for helium the element have completely filled s and P orbital(ns2np6) of the outermost shell general electronic configuration is Helium(1s2) , all these element are highly stable and chemical inert
2 representative element
all the element of s and p block with exception of noble gas are called representative element they represent to group alkali metal and alkaline earth metal on the extremely left and 5 group from 13 to 17 on the right hand side of the periodic table
3 Transition Element
the element of d block elements are called Transition Element these include element of group 3 to 12 line in between the representative element between s and p block
4 inner Transition
Element the element of a block are called inner Transition Element in this elements have , two series of 14 element called lanthanoid and actinoid
Cause of periodicity :-
the recurrence of similar properties of an atom of the element , after certain regular interval when they are arranged in the order of increasing atomic number is called periodicity
The classification of element in different group and families was depend upon the electronic configuration and also physical and chemical properties of the atom of the elemnt
But why do the similar properties recur at regular interval when all known element arrange in increasing sequence of atomic number in periodic table
The physical properties of the element depend upon the atomic mass of the element but chemical behavior of element depend upon number of electrons or atomic number but we know that it the properties of of element do not depend on the arrangement of electron in inner cell the chemical behavior of the element depend on arrangement of electron in the outermost cell are valency cell
For example the electronic configuration of first group are alkali metal show that the all an atom of the element of this group have one electron in their respected outer cell and this electrons occupy place in S- orbital and the general electronic configuration isns1
Li - 1s2 2s1
Na- 1s2 2s2 2p6 3s1
K - 1s2 2s2 2p63s2 3p6 4s1
Rb - 1s2 2s2 2p6 3s2 3p6 4s2 3d6 4p6 5s1
Cs - 1s2 2s2 2p6 3s2 3p6 4s2 3d6 4p6 5s2 4d10 5p6 6s1
Fr -1s2 2s2 2p6 3s2 3p6 4s2 3d6 4p6 5s2 4d10 5p6 6s2 4f14 . 5d10 6p6 7s1
On the basis of above👆 discussion it is clear that the all atom of the element arrange on the basis of increasing sequence of atomic number and also we found that after regular interval the similar outer shell electronic configuration is appeared that is the basic cause recur similar properties of element after definite intervals
And also it is observed 17 group halogen 👇family fluorine chlorine bromine iodine and astatine that was number 9 ,17, 35, 53 and 85
The outer shell electronic configuration of each atom of the element have 7 electron two electron in 2s orbital and five electron in p orbital does an electronic configuration of halogen family is ns2 and P5 Then all halogen family member show similar chemical behaviour because they have some outer cell electronic configuration(ns2 and p5)
Halogen family 👇
F - 1s2 2s2 2p5
Cl - 1s2 2s2 2p6 3s2 3p5
Br - 1s2 2s2 2p63s2 3p6 4s2 4p5
I - 1s2 2s2 2p6 3s2 3p6 4s2 3d6 4p6 5s2 5p5
At - 1s2 2s2 2p6 3s2 3p6 4s2 3d6 4p6 5s2 4d10 5p6 6s2 6p5
The repetition of similar electronic configuration of their atoms in the outermost energy level or valency cell after certain regular interval when atoms of the element are arrange increasing sequence of atomic number
this is the basic cause why after definite interval The recurrence of similar properties of the element In periodic table.
Atomic radius
Atomic radius means the distance from the centre of the nucleus to the electrons of outermost shell are valency shell
the size of the atom very small 1.2 X 10 - 10 m
according to atomic orbital concept the probability of finding electrons is never zero even at large distance from the nucleus
generally isolated atom not find out in our nature It exist in the form of
homo atomic or hetero atomic molecules form Then the size of atom also changed from one state to another
As H-H , H-Cl , H-O-H
in covalent molecules Internuclear distance two time (twice) from the radius of an atom that
is now as covalent radius
Covalent radius
one half of the distance between the nuclei of two covalently bonded atom of the same element in molecules
Homoatomic nuclear molecules
Internuclear distance Between two bonded atom
covalent radius = ……………………………………………………….
2
internuclear distance between two hydrogen atom in hydrogen molecules 74 pm then atomic radius of hydrogen 37 pm
internuclear distance two chlorine atom in chlorine molecules 198 pm then covalent radius of chlorine 99 pm
Covalent radius for heteronuclear molecules define as
In the heteronuclear molecules the distance between the centre of nucleus of the Two bonded an atom and the mean position of the shared pair of electron between the bonded atoms
H-Cl heteroatomic molecules
Metallic radius
in metallic lattice of metal the metallic atom closely packed and held together why metallic Bond
one half of the internuclear distance between the the two metallic Bond bonded neighbouring atoms of a metal in a metallic lattice
Example Internuclear distance between two atom in copper metallic lattice 256 pm therefore radius metallic of copper 128 pm
However l you are always remember that atomic or metallic radius, shorter than the atomic radii of atom in the uncombined form
Van Der waals radius
In the solid state One half of the internuclear distance between the nuclei of two adjacent atom of the molecular substance belonging to the two neighbouring molecules
The internet distance between two adjacent chlorine atom in the solid state 360 pm therefore Van Der waals radius but 180 pm
the covalent radius of chlorine 99 pm and Wonderwall radius 180 pm it means Van Der waals radius always greater than covalent radius
Ionic radius
The ions for ejection of electron and acquire positive charge are called Cations while ion form by accept of electron get negative charge are called a Anions
the effective distance from the centre of the nucleus of the ion up to which it has an influence in the ionic bond
in ionic compound
internuclear distance = radius of cations + radius of anion
example the inter nucleoid distance of sodium chloride 276 pm which corresponding to the sum of the ionic radii of sodium and chloride ions
(1)The radius of positive ions that time is always is smaller than that of the parent atom
The sodium cations Ionic radius 95 pm and sodium atom atomic radii 186 pm it means When sodium atom loss of one electrons and change into sodium cations then outer third shell of sodium atom disappear in sodium ions this is the cause why sodium cation smile size compare to sodium atom
Na → Na+ + e-
1s2,2s2,2p6,3s1 1s2,2s2,2p6,
186 pm 95 pm
(2)The Negative Ion is always larger than that of the corresponding atom
the Negative Ion is form When atom accept one or more Electron
an Chlorine atom accept of one electron and form chloride ion
The Chloride ion radius 181 pm but chlorine atomic radius 99 pm
Cl + e- → Cl- 1s2,2s2,2p6,3s2,3p5 1s2,2s2,2p6,3s2,3p6
99 pm 181pm
the Ionic radius of chlorine more than to chlorine atoms because when new electrons enter in their respected outer cell the inter electronic repulsion between electron - electrons increases and electrons disperse enlarge volume And also effective nuclear charge per an electron is reduced and the electrons cloud is held less tightly by the nucleus.
Verizon of atomic and ionic radii in the periodic table
variation in a period
the atomic radius on moving left to right in period gradually decrease because interaction between effective nuclear charge and electron increase
The atomic radius in period continuously decrease
But oxygen atomic radius more than to nitrogen because in case of oxygen(1s2,2s2,2px2py1pz1) the outer 2p subshell electronic configuration is responsible for electronic repulsion between electron and electron , electrons disperse enlarge volume because last electrons paired of 2P subshell electron and in nitrogen(1s2,2s2,2px1py1pz1) 2P subshell filled in unpaired form and electronic repulsion minimum
Variation in a group
On moving up to bottom in a group atomic radius are Ionic radius gradually increase because always Valence Electrons enter new energy level
Ionization enthalpy 👇
The energy required to removal an electron from outer cell are valency cell of isolated gaseous atom in its ground state
Ionization enthalpy is also known as ionization potential
the ionization enthalpies Express in unit of kilojoule per mole electron volt per atom or kilocalorie per mole
Example
Na → Na + + e- △H = +495.8 KJ/mol
Successive ionization enthalpy
The energy required to remove subsequent electron from outer shell or valence shell of an atom in the gaseous state are known as successive ionization enthalpy
the energy required for removal of first electron is called first ionization enthalpy after that the energy required removal of second electron from monovalent cations is called second ionization enthalpy and the removal of third electron from outer cell or valence shell from bi valent cations is called third ionization enthalpy
Example
The successive ionization enthalpy of magnesium
Mg → Mg++ + 2e-
(1) 1st ionization energy, 737.7 kJ⋅mol−1
Mg → Mg+ + e- △iH = +737.7 KJ/mol
First ionization enthalpy is the enthalpy change when most losely bonded electron is removed from valency our outer shell of of an isolated gaseous atom and first ionization enthalpy always less than 2 or third ionization enthalpy
(2) 2nd ionization energy, 1450.7kJ⋅mol−1;
Mg+ → Mg++ + e- △iH = + 1450.7 KJ/mol
Second ionization enthalpy as the energy required to removal of second-most loosely bonded electron from monovalent cations of the element
The second ionization enthalpy always greater than to first ionization enthalpy because after removal of one electron from valency shell atom can be changed monovalent cations , in Monovalent cations the attractions between outer shell electrons and nucleus increases compared to neutral gaseous atom because in outer shell after removal of one electrons , number of electron decrease but effective nuclear charge always constant then attractions between electrons of monovalent cations and nucleus increase then required energy removal of second electrons always more than two first ionization enthalpy
IE2 > IE1
2nd ionization energy, 1st ionization energy,
Of Mg 1450.7kJ⋅mol−1 > of Mg 737.7 kJ⋅mol−1
The successive ionization enthalpy of aluminium
Al → Al+++ + 3e-
(1) 1st ionization energy, 577 kJ⋅mol−1
Al → Al+ + e- △iH = +577 KJ/mol
(2) 2nd ionization energy, 1820 kJ⋅mol−1;
Al+ → Al++ + e- △iH = +1820 KJ/mol
(3) 3rd ionization energy, 2740 kJ⋅mol−1
Al++ → Al+++ + 3e- △iH = +2740 KJ/mol
Factor affecting of ionization enthalpy
(i) size of the atom
Enthalpy decrease with increase in size of an atom because the attractions force would been valency cell electron and in nucleus effective charge decrease as a result it becomes easier to removal of the electron from outer are valency celli
(ii) charge on the nucleus
increase with increase in nuclear charge because the treacherous force the attractions force increase between electron and nucleus when nuclear charge increases the removal of of an electron from isolated atom is difficult task
screening effect of the inner electrons
the The inner electrons always protect outer are valence shell electrons from attractions of nucleus , the protection of outer electrons from attractions of nucleus by the inner electrons is called screening effect or shielding effect
As a result of this outermost electrons does not feel full attraction force from the nucleus that actual attractions felt by an electrons is term as effective nuclear charge
(iii) Penetration effect of electrons
The S atomic orbital small in a size then the Penetration effect is highest compared to p d & f atomic orbital
S- atomic orbital penetrate more than p d & f atomic orbital and come to close of nucleus then the required energy for removal of electrons is always more than p - orbital, p-atomic orbital Penetration effect more than to d-orbital the required energy removal of p- electrons from p-atomic orbital always more than to d- atomic orbital
(iv) Electronic arrangement
it has been observed in periodic table that certain electronic configuration of an atom of the element are more stable than other for example half filled are complete field shell have extra stability associated with them
(according atomic orbital stability S1& s2 , p3& p6, d5& d10, f7& f14)
(1)The noble gas have the most stable electronic configuration ns2 and P6 in each period then the ionization enthalpy highest in in their respected period
(2) the second group are alkaline earth metal have stable outer electronic configuration ns2 then ionization enthalpy is also a large
(3) Nitrogen (1s2 ,2s2 2p3) phosphorus (1s2 ,2s2 2p6,3s2 3p3) atoms of the element have stable outer electronic configuration ns2 and np3 then the required large energy to removal of the electrons
The reason of ionization enthalpy in the periodic table
Verizon along A period👇
In general form the ionization enthalpy increase with increas eatomic number in a period because atomic size decrease and attractions Between outer shell electrons and nucleus increase because gradually one by one Proton inter in nucleus
But some irregularities find out when on moving across a period from left to right
As 👇
Boron (13 group ) ionization enthalpy +801 KJ/mol and beralium (2 group )first ionization enthalpy +899.5 KJ/mol it is less than to beralium first ionization enthalpy because in beralium (1s2 ,2s2 ) stable electronic configuration compare to boron (1s2 ,2s2 2p1) atoms of the element
nitrogen (15 group ) ionization enthalpy +1402.1 KJ/mol and oxygen (16 group ) first ionization enthalpy +1314 KJ/mol it is less than to nitrogen first ionization enthalpy because in Nitrogen (1s2 ,2s2 2p3) stable electronic configuration compare to oxygen (1s2 ,2s2 2p4) atoms of the element
Variation down a group👇
On moving down a group the ionization enthalpy decrease because gradually outer shell number increase means atom size increase then the attraction between outer shell electrons and nucleus decrease
Li △iH = +520 KJ/mol
Na △iH = +496 KJ/mol
K △iH = +419 KJ/mol
Rb △iH = +403 KJ/mol
Cs △iH = +374 KJ/mol
Electron gain enthalpy 👇
the energy released when extra electrons inter in in outermost cell of an
isolated gaseous atom the energy is called electron gain enthalpy and atom
change in Anion
As x + e- → x- △egH = …… KJ/mol
The energy released when electron is added to an isolated gaseous atom
Electron gain enthalpy process may be exothermic or endothermic
Example
(I) Electron gain enthalpy is exothermic process
F + e-→ F- △egH = -327.9 KJ/mol
O + e-→ O- △egH = --140.9 KJ/mol
(II) Electron gain enthalpy sometime Endothermic process
As
O- + e-→ O- - △egH = +780 KJ/mol
Successive electron gain enthalpy 👇
like ionization enthalpy the second and third electron gain enthalpy
are also possible
when extra electron inter in outer Shell or valence shell,
the electrons which already exist in outer shell always repel
incoming electrons then due to electron - electron repulsion
some energy always release It is called first electron get enthalpy
and this value
△egH = - KJ/mol ( or exothermic process )
Example
(1) oxygen first electron gain enthalpy 👇
O + e-→ O- △egH = --140.9 KJ/mol
(2) oxygen Second electron gain enthalpy :- 👇
The second electron gain enthalpy of oxygen positive or endothermic process
Because after addition of one electron oxygen change in
oxygen Monovalent anion, after that when one another electrons
enter in oxygen monovalent anions, The magnitude of electron - electron
Repulsion very high then extra force are extra energy required for
second electron which enter in monovalent anion
O- + e-→ O- - △egH = +780 KJ/mol
Therefore second electron gain enthalpy endothermic process and
first electron gain enthalpy exothermic process
Factor affecting of electron gain enthalpy👇
(i) Nuclear charge
Negative value of electron gain enthalpy depend on attractions between
incoming electrons and nuclear charge if nuclear charge more
than electron gain enthalpy have large value
(ii)Size of the atom
Electron gain enthalpy depend on attractions between incoming
electrons and nucleus, if size of the atom small then attractions between
electrons and nucleus is higher means electron gain enthalpy have
large value
(iii) Electronic configuration
17 group ( halogen family ) member have higher electron gain enthalpy
in their respect period because they have ns2 and P5 electronic configuration
only one electrons required for complete of their octet
1 group (alkali metal) have smaller electron gain enthalpy because the have
general electronic configuration ns1 they have tendency to release or
lose of one electrons instead of gain of electron
Periodic trends of electron gain enthalpy 👇
variation in A period 👇
On moving in period left to right generally electrons gain enthalpy increase
because Atomic size decreases and attraction between electrons and nucleus
increases Then incoming electrons felt more attraction towards the side of the
nucleus.
variation down a group 👇
On moving down a group the size and nuclear charge increase but the effect of
increase in atomic size it's much more compared to nuclear charge.
Then incoming electrons feel less attractions by the nucleus in large size atoms
then electron gain enthalpy decreases .
Some important point (variation) 👇Halogen have the highest negative electron gain enthalpy :- 17 group
( halogen family ) member have higher electron gain enthalpy in their
respect period because they have ns2 and P5 electronic configuration. only one electrons required for complete of their octet.
Electron gain enthalpy of noble gas are positive :- 18 group (noble gas or real gas or inert gas ) have completed octet of their valency or outer shell.
No need of of extra electrons because octet complete. if any additional
electrons inter in any noble gas definitely it occupy place in new outer valency cell and it feel less attraction by the nucleus this is the cause why electron gain enthalpy of noble gas have positive value.
Beryllium magnesium of alkaline earth metal and nitrogen Phosphorus of of 15 group have zero electron gain enthalpy :-
Electron gain enthalpy of beryllium (2s2) and magnesium (3s2) almost is
zero because they have stable ns2 electronic configuration.
electron gain enthalpy of of Nitrogen (2s 2 2p3) and phosphorus
( 3s 2 3p3 )almost is zero because they have stable ns 2 np3 electron
configuration
Electron gain enthalpy of fluorine (−333kJ/mol)is unexpectedly less negative than that of chlorine (−349kJ/mol)
it is observed that fluorine atom has unexpected less negative electron
gain enthalpy than chlorine atom because fluorine atom very small in size
therefore incoming electrons feel much more inter electronic repulsion
in the relative compact 2P subshell of fluorine atom but in the case
of chlorine outer shell third Then incoming electron not fell
more inter electronic repulsion in the relative large in 3P subshell
And also the attraction between incoming electrons and the
nucleus is much more in Cl-atom
F + e-→ F- △egH = -333. KJ/mol
Cl + e-→ Cl- △egH = -349 KJ/mol
write chapter name in comments box for reading notes or question bank according new CBSE pattern👇