CLASS :- 11
Topic :-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.
