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9 Class- Atomic Structure

Atomic Structure

What is an atom?

Matter found around us in nature (like iron rod, glass, cup, pen, pencil etc.) is made up from very small particles, which is known as atoms.
we also says that "atoms are very small particles which made matter" so atom is fundamental unit of atom.

Greek Philosopher, Democritus describe atom as very small indivisible particle.

'New System of Chemical Philosophy' is a book about atom written by John Dalton in 1703.

Dalton Atomic Theory

According to this theory atom cannot be divided, but after some years it is proved that atom can be divided further by many scientists like J.J.Thomson, L.Rutherford, N.Bohr, Chadwick etc.

Constituting particles of atom

Atom made up from 3 main particles-
1. Electron 2. Proton 3. Neutron

Discovery of Electron

Sir J.J.Thomson and W.Crooks did many experiments with discharge tube for the discovery of electron.
Discharge tube have tube like shape made from glass with two electrodes (Cathode -ve and Anode +ve) in vacuum created by vacuum pump connected to discharge tube. High electric potential is applied between two electrodes.
9th class chemistry notes of structure of atom - Discharge Tube 
Discharge Tube
Air is bad conductor of electricity so vacuum pump is connected to reduce pressure to 0.02mm inside discharge tube currents starts flowing between electrodes and light is emitted. On further reducing pressure in discharge tube greenish yellow color fluorescence occur. As these rays emerging from cathode, Sir J.J.Thomson named them as cathode rays.
Deflection of cathode rays towards positively charged plate in electric field proves that these rays carry negatively charged particles.
These negatively charged particles are named as electrons.

Properties of Cathode Rays

1. Cathode rays always travel in straight line.
Production of Cathode Rays
2. Velocity of cathode rays and velocity of light are approximately equal.
3. On applying electric field in the path of cathode rays, cathode rays turn towards +vely charged plate that proves cathode rays are made up from negatively charged particles.
4. Cathode rays rotate light wheel placed in their path that proves cathode rays are made from particles having mass.
5. Cathode rays pass through thin metal foil and it gets slightly heated up by action.
6. These rays produce fluorescence at walls of glass tube.
7. Cathode rays ionize gases and also affect photographic plate.
8. When these rays strike any metal with high melting point (like tungsten W) they produces X-Rays.

What is X-rays?

X-rays are electromagnetic radiation , X-rays was discovered by W.K.Roentgen in 1895. X-rays are also known as Roentgen rays.

Why X-rays are used in medical sciences?

X-rays are used in medical sciences because x-rays have high penetrating power.

Determination of charge to mass ratio of electron (e/m)

J.J.Thomson conduct many experiments that charge to mass ratio of an electron remains same, irrespective of nature of gas and nature of cathode electrode material.
value of e/m = -1.76x108 coulombs/gram

Millikan's Oil Drop Experiment

Millikan's Oil Drop Experiment or Determination of charge of electron is conduct by an American Scientist R.A.Millikan, who perform an experiment on the charge on oil drops. R.A.Millikan perform several experiments to calculate charge on oil drops and he gets every time its value equal to -1.6x10-19 coulomb.When these results associated with results of cathode rays then conclude that charge present on particle of cathode rays is -1.6x10-19 coulomb.

Calculation of mass of electron

As we  know e/m = -1.76x108 coulombs/gram
                          e = -1.6x10-19 coulomb
then,
              (e/m)/e = (-1.76x108)/(-1.6x10-19)
so,
                       m = 9.102x10-28 gram
                       m = 9.102x10-31 kilogram

Mass of electron in comparison with atom

Mass of electron in comparison with atom is described below-
Mass of 1 mole of Hydrogen = 1.008gms
Number of hydrogen atom in 1 mole = 6.023x1023
Mass of 1 atom of hydrogen = 1.008/6.023x1023
                                             = 1.67x10-27kg
Mass of electron is 9.109x10-31
then,
                         =  Mass of 1 atom of hydrogen/Mass of electron
                         = (1.67x10-27)/(9.109x10-31) = 1837
so,
     Mass of an electron is 1/1837 th the mass of a hydrogen atom.

Discovery of Proton

As we know electron is negatively (-vely) charged particle but atom is electrically neutral so there should be some particles which have positive (+ve) charge to neutralize negative (-ve) charge electron.
In 1886, a German scientist E.Goldstein established the presence of +vely charged particles. These positively charged rays travel from anode to cathode so called as anode rays or positive rays.

Why anode rays are called as canal rays?

Anode rays passes through canals or perforation in cathode so called as canal rays.

Properties of Anode Rays

1. Anode rays always travel in straight line.
2. Anode rays rotate light wheel placed in their path that proves anode rays are made from particles having mass.Which produces mechanical action.
 3. On applying electric field in the path of anode rays, anode rays turn towards -vely charged plate that proves that anode rays are made up from positively charged particles.
Production of Anode Rays

Determination of charge to mass ratio of proton (e/m)

On the basis of many experiments performed for anode rays, scientist Wein concluded that charge to mass ratio of proton changes with change in nature of gases present in discharge tube. This value (e/m) is maximum for hydrogen gas = 9.58x104 coulomb per gram. "Positively charged particle of hydrogen is fundamental particle of matter that is called proton."

Charge on proton

Charge on proton is equal to charge on electron but is of opposite nature.
Charge on proton = 1.602x10-19 coulomb.
Mass of the proton
For hydrogen gas,
                       e/m = 9.58x104 coulomb per gram
charge of electron = 1.602x10-19 coulomb
so,
    m = (e)/(e/m) = (1.602x10-19)/(9.58x104)
also,
      m = 1.67x10-24 gram
      m = 1.67x10-27 kg
so,
     mass of proton is 1837 times more than mass of electron and is equal to mass of an hydrogen atom.

Discovery of Neutron

Mass of atom is more than the mass of total proton and electron present in atom, which suggest the presence of another particle in atom which lead the discovery of neutron.
 Chadwick in 1932 discover neutral particles of mass equal to mass of proton by bombarding beryllium metal with stream of fast moving particles through cyclotron. These particle are neutral in nature so named as neutron.
Mass of neutron = 1.6748x10-27 kg

There is three fundamental particles in atom

These fundamental particles are 1. Electron 2. Proton 3. Neutron

Many atomic models are proposed from time to time to show the actual structure of atom, some of them are described below-
1. Thomson's atomic model
2. Rutherford's atomic model
3. Bohr's atomic model

Thomson's Atomic Model

Thomson's Atomic Model
Thomson's atomic model is first atomic model proposed in 1898 related to atomic structure. This model is similar to water-melon in which positive charge protons is like pulp in which negative charge electrons like seeds in water-melon, also known as pudding model. This model is called Thomson's atomic model.

Drawback of Thomson's atomic model

Thomson's atomic model is unable to explain scattering experiment of Rutherford.

Rutherford Model of Atom

This experiment is also known as alpa () particle scattering experiment. Rutherford bombard alpha particle on gold foil of thickness 0.0004cm and found that-
1. So many particles passes through the gold foil without any deflection.
2. Some alpha particle are deflected at different angles.
3. Very few about 1 in 20,000 are bounced back (at 360 degree) from gold foil.

Rutherford Atomic Model
Rutherford concluded nuclear model of atom as-
1. Most of the part of the atom is hollow and neutral so alpha particles passes straight without any deflection.
2. All positive charge is present in center of atom so alpha particle are deflected at different angles by repulsion from positively charged center known as nucleus.
3. Only very few particles bounced back so size of nucleus is very small as compared to size of atom.
4. Electron moves around nucleus like planet moves around sun in orbits.
5. Mass of electron is negligible so all mass of atom is present in nucleus.
6. Atom is electrically neutral so number of electron is equal to number of proton present in atom.

Defects of Rutherford Atomic Model

1. Stability of atom is not explained on the basis of this model.
2. This model could not explain discrete spectrum.

Bohr's Atomic Model

Neils Bohr in 1913 gives a simple model for atomic structure based on the quantum theory.
Main assumption of Bohr atomic model-
1. All atoms consist of dense, very small, positively charged nucleus that have all protons and neutrons in it.
2. Electron revolve around nucleus in definite energy paths known as orbits, shell or energy levels.
3. Orbits denoted by (n). value of n is whole number 1,2,3,4.......... etc. which are represented as K,L,M,N............. etc. respectively.
Bohr Atomic Model
4. As we increase the value of n the orbit move farther from nucleus (means distance between nucleus and orbit of higher n is more than smaller n) and their energy also increases so n=1 or K shell have lowest energy.
5. If an electron revolve in same energy level then their is no change in its energy level.
6. As electron absorb energy from outside, it gets exited and move to higher energy level and come back after emitting energy to lower energy level.
9th class chemistry notes of atomic structure
Absorption and Emission of Electron Energy

Atomic Number

Number of protons present in nucleus of atom of an element is known as atomic number.
It is denoted by (z)
example : Carbon have 6 protons so its atomic number is 6 (z = 6)
For neutral atom,
 atomic number (z) = number of protons (p) = number of electron (e)

Number of protons in cation > Number of electrons in cation
Number of protons in anion < Number of electrons in anion
Number of protons in neutral atom = Number of electron in neutral atom

Mass Number

Mass number is also known as atomic mass. Atomic number or mass number is equal to number of protons and neutrons in atom.
Atomic mass = number of protons + number of neutrons
                 A = p+n
example : Helium have two protons and two neutrons so its atomic mass is 2+2=4

Isotopes

Atoms of same elements which have same atomic number but different mass number is called isotopes.
example : Protium, Deutrium, Tritium are isotopes of hydrogen.

Types of Isotopes

1. Non-radioactive isotope example C(12), C(13)
2. Radioactive isotopes example U(235), U(233), U(238), U(239)

Isobars

Atoms of different elements which have similar atomic mass and different atomic number are called isobars.
example : Ca(40), Ar(40), Kr(40)
                 50Cr24, 50Ti22
Isobars do not similar in physical and chemical properties

Distribution of electrons in various orbits : ( Bohr Bury  Scheme )

In 1921, Bohr and Bury gives some laws for distribution of electrons in various orbits, which are called as Bohr-Bury Scheme.
Rules of Bohr Bury scheme are as follows-
1. Maximum number of electron in any shell should be 2n2 , where n is serial number of shell.
2. Maximum number of electron that exist in outermost shell or orbit of any atom is eight while maximum number is eighteen for penultimate shell.
3. According to this law, it is not necessary that another shell is formed after completion of 1st shell. A new shell is formed as number of electrons reaches eight in any orbit or shell.

Valence Electrons and Valency

 Outermost incomplete shell of any atom is known as Valence Shell and electron present in incomplete outermost shell are known as Valence Electrons , which participate in formation of bond.
  • If atoms have 1 to 4 valence electrons then VALENCY = Number of valence electron
  • If atoms have 5 to 8 valence electrons then VALENCY = 8 - Number of valence electron
  • But these above rule is not applicable to atoms which show variable valency

Radioactivity

Radioactivity is discovered by French scientist Becquerel in 1896. Substances which emits radiation is known as radioactive substances and this property of substances to emit radiation is called as radioactivity.
example : Uranium exhibit radioactivity.

Rutherford conduct some experiments with radioactive substances and his observations are as follows-
1. Rays which turned toward negative electrode is known as alpha rays, mass of alpha particles is 4 a.m.u.  and charge is 2 units of positive charge.
2. Rays which turned toward positive electrode is known as beta  rays, mass and charge of beta particle is equal to mass and charge of electron.
3. The rays which do not turned towards any electrode is known as gamma  rays, gamma rays are electromagnetic rays and not made from matter particle.

Penetrating Power

Gamma > Beta > Alpha
Gamma rays have maximum penetrating power while Alpha has lowest.

Tracer technique of radioactive isotopes

As per requirement, small amount of radioactive isotopes is added to its element then many physical and chemical complex reaction are studied.

Various fields of tracer techniques

  1. In the field of chemical science.
  2. In the field of medical science.
  3. In the field of agriculture.
  4. In the industrial fields.
  5. And in other scientific fields.

Carbon Dating

In this technique carbon isotope is used to determine the age of rocks, minerals, fossils, dead animals and dead plants.

Discovery of Neutron

Discovery of Neutron

Mass of atom is more than the mass of total proton and electron present in atom, which suggest the presence of another particle in atom which lead the discovery of neutron.
 Chadwick in 1932 discover neutral particles of mass equal to mass of proton by bombarding beryllium metal with stream of fast moving particles through cyclotron. These particle are neutral in nature so named as neutron.
Mass of neutron = 1.6748x10-27 kg

There is three fundamental particles in atom

These fundamental particles are 1. Electron 2. Proton 3. Neutron

Discovery of Proton

Discovery of Proton

As we know electron is negatively (-vely) charged particle but atom is electrically neutral so there should be some particles which have positive (+ve) charge to neutralize negative (-ve) charge electron.
In 1886, a German scientist E.Goldstein established the presence of +vely charged particles. These positively charged rays travel from anode to cathode so called as anode rays or positive rays.

Why anode rays are called as canal rays?

Anode rays passes through canals or perforation in cathode so called as canal rays.

Properties of Anode Rays

1. Anode rays always travel in straight line.
2. Anode rays rotate light wheel placed in their path that proves anode rays are made from particles having mass.Which produces mechanical action.
 3. On applying electric field in the path of anode rays, anode rays turn towards -vely charged plate that proves that anode rays are made up from positively charged particles.
Production of Anode Rays

Determination of charge to mass ratio of proton (e/m)

On the basis of many experiments performed for anode rays, scientist Wein concluded that charge to mass ratio of proton changes with change in nature of gases present in discharge tube. This value (e/m) is maximum for hydrogen gas = 9.58x104 coulomb per gram. "Positively charged particle of hydrogen is fundamental particle of matter that is called proton."

Charge on proton

Charge on proton is equal to charge on electron but is of opposite nature.
Charge on proton = 1.602x10-19 coulomb.
Mass of the proton
For hydrogen gas,
                       e/m = 9.58x104 coulomb per gram
charge of electron = 1.602x10-19 coulomb
so,
    m = (e)/(e/m) = (1.602x10-19)/(9.58x104)
also,
      m = 1.67x10-24 gram
      m = 1.67x10-27 kg
so,
     mass of proton is 1837 times more than mass of electron and is equal to mass of an hydrogen atom.
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Millikan's Oil Drop Experiment

Millikan's Oil Drop Experiment

Millikan's Oil Drop Experiment or Determination of charge of electron is conduct by an American Scientist R.A.Millikan, who perform an experiment on the charge on oil drops. R.A.Millikan perform several experiments to calculate charge on oil drops and he gets every time its value equal to -1.6x10-19 coulomb.When these results associated with results of cathode rays then conclude that charge present on particle of cathode rays is -1.6x10-19 coulomb.

Calculation of mass of electron

As we  know e/m = -1.76x108 coulombs/gram
                          e = -1.6x10-19 coulomb
then,
              (e/m)/e = (-1.76x108)/(-1.6x10-19)
so,
                       m = 9.102x10-28 gram
                       m = 9.102x10-31 kilogram

Mass of electron in comparison with atom

Mass of electron in comparison with atom is described below-
Mass of 1 mole of Hydrogen = 1.008gms
Number of hydrogen atom in 1 mole = 6.023x1023
Mass of 1 atom of hydrogen = 1.008/6.023x1023
                                             = 1.67x10-27kg
Mass of electron is 9.109x10-31
then,
                         =  Mass of 1 atom of hydrogen/Mass of electron
                         = (1.67x10-27)/(9.109x10-31) = 1837
so,
     Mass of an electron is 1/1837 th the mass of a hydrogen atom. 
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Discovery of Electron

Discovery of Electron

Sir J.J.Thomson and W.Crooks did many experiments with discharge tube for the discovery of electron.
Discharge tube have tube like shape made from glass with two electrodes (Cathode -ve and Anode +ve) in vacuum created by vacuum pump connected to discharge tube. High electric potential is applied between two electrodes.
9th class chemistry notes of structure of atom - Discharge Tube 
Discharge Tube
Air is bad conductor of electricity so vacuum pump is connected to reduce pressure to 0.02mm inside discharge tube currents starts flowing between electrodes and light is emitted. On further reducing pressure in discharge tube greenish yellow color fluorescence occur. As these rays emerging from cathode, Sir J.J.Thomson named them as cathode rays.
Deflection of cathode rays towards positively charged plate in electric field proves that these rays carry negatively charged particles.
These negatively charged particles are named as electrons.

Properties of Cathode Rays

1. Cathode rays always travel in straight line.
Production of Cathode Rays
2. Velocity of cathode rays and velocity of light are approximately equal.
3. On applying electric field in the path of cathode rays, cathode rays turn towards +vely charged plate that proves cathode rays are made up from negatively charged particles.
4. Cathode rays rotate light wheel placed in their path that proves cathode rays are made from particles having mass.
5. Cathode rays pass through thin metal foil and it gets slightly heated up by action.
6. These rays produce fluorescence at walls of glass tube.
7. Cathode rays ionize gases and also affect photographic plate.
8. When these rays strike any metal with high melting point (like tungsten W) they produces X-Rays.

Baeyer Villiger Oxidation

Baeyer Villiger Oxidation Reaction

Baeyer Villiger Oxidation
Baeyer Villiger Oxidation

The Baeyer Villiger Oxidation is  a oxidation reaction in which oxidative cleavage of a C-C bond near to a carbonyl group happen, which leads to conversion of ketone to ester or cyclic ketone to lactone. Baeyer Villiger Oxidation may be carried out with peracids like MCBPA or with  a Lewis acid and Hydrogen Peroxide.

Mechanism of Baeyer Villiger Oxidation

Mechanism of Baeyer Villiger Oxidation
Mechanism of Baeyer Villiger Oxidation

BSc1Year Atomic Structure

Atomic Structure

Atom:

          In Greek Atom means not divided. In 1803 john Dalton made a famous theory atomic theory according to this theory “matter is made up of tiny particles called atoms.” But in 1897 Sir J.J. Thomson proved experimentally that atoms are made of charged particles called electrons. And in the beginning of 20th century many scientists like Lord Rutherford, E. Goldstein proved that atom is not a smallest particle but is made up of electron, protons and neutrons.
De-Broglie’s equation:  
According to the plank’s photon of light having energy E and frequency n.
Then               E = hn                        …………………………………………….(1)
According to Einstein Mass, energy relation is
                        E = mc2                             ………………………………………(2)
Where c is velocity of light
Combining both above equations (1) & (2) we get
                                                    hn = mc2
Then                                            
 Or                                   
Or                                     
This equation for photon, when we put v in place of velocity of light c it becomes.
                                               
This equation is known as de-Broglie equation.
           
Since h is constant and p is momentum (mv) of particle.
Then                          
de-Broglie equation is applicable to electron, proton, neutron, atoms, molecules etc. and is also applicable to calculate wavelength of moving material particles if velocity is known.

BSc2Year Chemistry of Elements of First Transition Series

Chemistry of Elements of First Transition Series

There are four types of orbital i.e. s, p, d and f. On the basis of electronic configuration-
·         s-block elements : last electron goes in s orbital.
·         p-block elements : last electron goes in p orbital.
·         d-block elements : last electron goes in d orbital.
·         f-block elements : last electron goes in f orbital.

Transition Elements: -  

                              The elements of d-block which act as bridge or transit point between s and p-block elements is known as transition elements.
d-block elements have four series :

1.      First transition series :- 

                                      This series contains elements from atomic number 21 (scandium) to atomic number 30 (Zinc). It is called 3d series because last electron goes in 3d orbital. And it is present in fourth period of periodic table.

2.      Second transition series :- 

                                           This series contains elements from atomic number 39 (Yttrium) to atomic number 48 (cadmium). It is called 4d series because last electron goes in 4d orbital. And it is present in fifth period of periodic table.

3.      Third transition series :- 

                                           This series contains elements 57 (Lanthanum) and from atomic number 72 (Hafnium) to atomic number 80 (Mercury). It is called 5d series because last electron goes in 5d orbital. And it is present in sixth period of periodic table.

4.      Fourth transition series :- 

                                      This series contains Actinium (89) and element with atomic  number 104 (Rutherfordium) and all above series elements. It is called 6d series. And it is present in sixth period of periodic table. All the elements other then Actinium in this series are synthesised.

Characteristic Properties of d-block elements : 

                                                               Main characteristics of d-block elements are as follow:

Physical state and metallic properties : 

                                                     All d-block elements are solid except Mercury. Mercury is present in liquid state. Atoms of d-block elements have maximum 2 electrons in outermost shell so they show metallic character. Unlike s-block elements these are rigid, malleable and ductile. D-block elements are good conductor of heat and electricity. and have metallic lustre.

Melting point and Boiling point :  

                                               These have high Melting and high Boiling point due to stron bond between elements. Zn, Cd and Hg have low Melting and low Boiling point due to completed sub-orbit.

Atomic radius :  

                      In periods of d-block elements, atomic radius generally decreases with increase in atomic no. It is due to increase in nuclear charge of atoms in a period.

Ionic radius : 

             d-block elements form cations which are smaller than its corresponding atoms. Ionic radius generally decreases across a period with increase in atomic no.

Atomic volume :  

                     Atomic volume of the d-block elements is low as compared to near s and p block elements. Atomic volume decreases with increase in atomic number in a period, but after acquiring a minimum volume it increases due to increased screening effect.

Density : 

          In a period of d block elements gradual increase in density take place with increase in atomic no. And density decreases after acquiring maximum value due to increase in atomic radius and atomic volume.

Standard Electrode Potential : 

                                          Standard Electrode Potential of hydrogen is assumed to be zero. Standard Electrode Potential of other electrodes is determined relative to Standard Electrode Potential of hydrogen.

Ionization Potential :  

                              Ionization Potential of d-block elements is intermediate between s and p block elements. Ionization Potential value increases with increase in atomic number across a period.

Electropositive character : 

                                      d-block elements are electropositive, but as compared to s-block elements these are less electropositive. So form electrovalent compound with more difficulties as compared to s-block elements.

Electronegativity : 

                         Electronegativity of transition elements increases with increase in nuclear charge. Last element of each period have complete d sub-shell so have low electronegativity value because screening effect of complete d sub-shell is more than incomplete d sub-shell.

Oxidation states : 

                        d-block elements show variable oxidation state. Electrons in d orbital are responsible for variable oxidation state. +2 oxidation state occur on removal of two s electron from outermost shell. Other oxidation state (i.e. more than +2) require removal of electron of d orbital of penultimate shell.

Complex formation : 

                          Due to incomplete d sub-shell of d-block elements they are able to form complex compounds. Central ion is capable to accept lone pair of electron donated by ligands to form complex. Empty orbital in a atom adjust these lone pair of electrons. According to Pauling, Transition elements either have empty orbitals or they produced empty orbital when surrounded by the ligands.

Catalytic character :  

                          d-block elements or their compounds are used as a catalyst in many chemical reactions. Generally Fe, Cr, Pt, Ni, V2O5, Mn etc., are used as a catalyst. A essential property of a catalyst is to form an unstable intermediate. Due to various oxidation state transition elements form intermediate easily. Good catalyst have free valency on its surface. Catalyst are used in finely divided form to increase surface area to attain increased number of free valancy.

Alloy formation : 

                       Due to approximately equal size of d-block elements they form alloy.

Reactivity : 

                d-block elements are less reactive due to higher ionization potential (because of smaller atomic size), so hydration of cations of d-block elements is difficult and have high heat of sublimation.

Formation of Interstitial or non-stoichiometric compounds :  

                                                                                              Compounds which do not follow valency rule are known as non-stoichiometric compounds. These type of compound are formed due to entrance of the non-metallic atoms into the interatomic spaces of metal atoms. Eg. TiH1.7, VSe0.98, FeO0.94, etc.

Coloured Ions : 

                   Compounds or Ions of transition elements appear to be coloured due to these reasons-
(i)                 d-d transition
(ii)               charge transfer

(i)                 d-d transition : 

                                          In a compound of d-block element colour depend on transition of electron from lower energy level to higher energy level and in ion of d-block elements, due to unpaired electron in d orbital, it get splitted into two parts at the time of complex formation.  These two orbital differ in their energies. Electron absorb radiations in visible region and transition of electron occur from lower energy level to higher. So colour of transition elements depends on d-d transition. Also If no of d-d transition is higher then colour of ion is darker.

(ii)               charge transfer : 

                                          d-d transition is not possible in PbO2, MnO4-, Cr2O72-, Sn2+ and Sn4+ etc. No unpaired d electrons are found in them. In these ions transition of electrons occur from orbital of one atom to orbital of another atom by absorbing radiation to produced dark colour. This transition occur in UV region (1800  - 4000 ) is known as charge transfer transition.

Magnetic Properties : 

                              On the basis of magnetic behaviour they are classified into five categories
(i)                 Diamagnetic
(ii)               Paramagnetic
(iii)             Ferromagnetic
(iv)             Antiferromagnetic
(v)               Ferrimagnetic

(i)                 Diamagnetism: 

                                      The type of substance which when placed in a magnetic field the intensity of magnetic field decreases as compared to the intensity in vacuum the substances are known as diamagnetic substances and this property is called diamagnetism.
Diamagnetism is due to the presence of paired electrons hence found in all substances except hydrogen. Magnetic lines of force tends to move away from the substances so these substances are repelled by magnetic field and these substances align themselves at right angle to magnetic field. Diamagnetism is occurs due to the presence of paired electrons. In this type of substances magnetic moment produced by one electron is cancelled by another which is equal and opposite to first one. So no magnetic moment present in substances having paired electrons.
Diamagnetism increases with increase in atomic number.

(ii)               Paramagnetic : 

                                      It is found in substances which have unpaired electrons like transition elements. This type of substances having permanent magnetism. When this type of substances placed in external magnetic field, they aligns themselves in the direction of magnetic field. Paramagnetism occurs due to motion and spin of electrons. Paramagnetism decreases with increase in temperature. These types of substances are attracted in magnetic field. If number of unpaired electrons in a substance is n then magnetic moment.
                                           
                   Number of unpaired electrons in substances is calculated by the magnetic.

(iii)             Ferromagnetism: 

                                        Substances which have very high paramagnetic character are known as ferromagnetic substances. And found in some alloys or compounds of Fe, Co, Ni, Mn. These types of substances even remain magnetic characters after removing from the external magnetic field. This type of substances contains tiny magnets in them which arrange randomly. On placing this type of substances in magnetic field these tiny magnets arrange them in one direction so these show very high magnetism.

(iv)             Antiferromagnetism: 

                                      These types of substances do not show magnetism (Paramagnetism) even they have unpaired electrons like MnF2, MnO.

 Properties of elements of first transition series:

Elements from Sc (21) to Zn (30) are known as elements of first transition series (i.e. 3d transition series). In the atoms of first transition series last electron goes in 3d sub-sell.

Binary Compounds

The compounds which are formed by two types of elements and ions are known as binary compounds. Elements of the first transition series react with so many non metallic elements like carbon, oxygen, phosphorus, sulphur and nitrogen etc. to form binary compounds. Oxides, halides, sulphides, carbides are main binary compounds of first transition series.

Oxides: -  

          When element of first transition series heated with oxygen at high temperature metal oxides are formed. Important oxides of first transaction series are as follows.
Acidic  oxides : V205, CrO3, MnO3.
Basic Oxides : Sc2O3, TiO, Ti2O3, VO, V2O3, MnO, CrO, FeO, Fe2O3, Fe3O4, CoO, NiO, Cu2O.
Amphoteric Oxides : TiO2, VO2, Cr2O3, CrO2, Mn3O4, Mn2O3, MnO2, CuO, ZnO.
Main properties of oxides :
1.      Acidic, Basic or Amphoteric nature : As the oxidation No. of metal increases its acidic nature of oxides also increases.

Oxides of Vanadium              VO                  V2O3              VO2                V2O5
Oxidation No. of vanadium   +2                    +3                    +4                    +5
Nature of oxides                     Basic               Basic        Amphoteric            Acidic

2.      Solubility : Amphoteric and basic oxides are soluble in acids which do not act as oxidants. Acidic oxides form oxy acids in water and oxy salts in bases to get dissolved.
3.      Reducing nature of oxides : Electron donor substances act as  reductant. Substances (atoms, ions and molecules) which donate their electrons easily have higher reducing character.
Halides : Elements of first transition series (3d series) react with halogens at high temperature to form halides. Order of reactivity of halogens with the metals is as given below.
                                                F2 >Cl2> Br2> I2
Generally fluorides formed in higher oxidation states. Formation of halides require high activation energy so this reaction occurs at high temperature.
Properties of halides
1.      Transition metal halides are less volatile and more susceptible to hydrolysis. Metal halides in higher oxidation states have high tendency to undergo hydrolysis.
TiCl4 + 2H2O ® TiO2 + 4HCl
2.      In lower oxidation states more stable oxides are formed.
Eg. :ZnCl2, VCl2 etc.
3.      Fluorides are ionic in nature. Chlorides, Bromides and iodides have both ionic and covalent character.
Fluoride > Chloride > Bromide > Iodide

Sulphides : 

                Sulphides are obtained on heating metal with sulphur. Metal sulphides are also produced on reacting aqueous solution of metal salts with Na2S or H2S.
Properties of sulphides :
1.      First transition metal sulphides are mainly dark colored or black.
CuS – Black
NiS – Black
CoS – Black
2.      Sulphides are insoluble in water.
3.      They get oxidised to metal sulphates on oxidation.
4.      Some sulphides such as CoS, NiS and FeS behave as an alloy or exibit the semi-metallic character.
5.      FeS2, CoS2 contain discrete S2 units with S-S bonding.
Carbides : carbides are produced on heating transition metals or metal oxides with carbon at very high temperature about 2000-2200°C.
Carbides formed by first transition series elements are of two types-
(a)    Salt like carbides : These carbides are also known as electrovalent carbides or ionic carbides. Metals like Sc, Cu, Zn etc. form this type of carbides.
(b)   Interstitial Carbides : These carbides are also known as metallic carbides. Metals like Ti, V, Mn, Fe, Co form such type of carbides. These type of carbides are obtained on heating a carbon and metal..
Properties of interstitial carbides
1.      interstitial carbides are extremely hard.
2.      interstitial carbides have high melting point.
3.      interstitial carbides have high electrical conductivity.
4.      interstitial carbides show inertness to chemical reactions.
5.      interstitial carbides have metallic lustre.
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