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8/3/2019 Chapter -1 Fundamental of Chemistry
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Chapter -1 Fundamental of
Chemistry There are three fundamental particles
posses in an atom named Electron,
Proton and Neutron respectively.
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Electron It was discovered by J.J. Thomson.
It is a negatively charged particle.
Its mass is 9.108x10-31 kg.
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Proton It is a positively charged particle.
Its mass is 1.672.10-19kg.
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Neutron It was discovered by Chadwick.
It is neutrally charged particle.
Its mass is equal to proton.
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Atomic Nucleus The central part of an atom which
consists proton and neutron is called as
Atomic Nucleus.
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Atomic Number The number of planetary electrons in an
atom is called as Atomic Number.
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Mass Number The sum of the number of Protons and
Neutron is called as Mass number.
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Bohrs Atomic Model Electrons in an atom revolve round the nucleus in circular
orbits.
The circular orbits are stationary and having constantenergy.
Emission or absorption of energy by electron will be inquanta. While doing so electron jumps from one orbit toother.
The energy emitted or absorbed will be equal to thedifference in energies of the two orbits.
The angular momentum of the electron revolving in astationary orbit is equal to integral multiples of h/2.
mvr =nh/2
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Limitations of Bohrs Atomic
Model Bohrs theory could not explain the atomic
spectra of higher elements such asHe,Li,Be,B,Cwhich have more than one
electron. Bohrs theory did not provide any
explanation for union of atoms to formmolecules.
Bohrs theory could not explain the ZeemanEffect. Bohrs model could not justify the
quantization of angular momentum.
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Quantum Numbers Quantum numbers are used for knowing the
position, energy, angular momentum, shape,
etc of an atom. There are four types of Quantum Numbers: -
Principle Quantum Number (n)
Azimuthal Quantum Number (l) Magnetic Quantum Number (m)
Spin Quantum Number (s)
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Principal Quantum Number(n) Principal quantum number gives thew
size and energy of the orbit and
indicates the main energy level. It hasvalues 1,2,3,4,.and are also indicatedby K,L,M,N
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Azimuthal Quantum Number() Azimuthal quantum number indicates
the number of possible sub-levels in
each energy level. can take valuesfrom O to (n-1)a total n values where
n is the principal quantum number.
Values of =(0,1,2,3) aredonated by s,p,d,f.
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Magnetic Quantum
Number(m) m determines the orientation of
orbits in space. It also gives the
number of orbitals in each sub level.The permitted values are dependingupon the l. For a given value of the
values of magnetic quantum numberare given by - or + including O.
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Spin Quantum Number(s) Spin quantum number(s) is due to
spinning of e- . The e- spin may be
either in the clockwise () oranticlockwise direction ().
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Paulis Exclusion Principle No two electrons of the dame atoms
can have the same values for all the
quantum numbers.
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Aufbau Principle
According to Aufbaus principle e- tendto occupy orbitals of minimum energy
and the orbitals with lower energy arefilled first before filling of orbitalshaving higher energy starts.
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Hunds rule
Pairing of e- takes place when all theavailable degenerate orbitals are
occupied by one e- each.
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Orbit
Orbit is a circular path followed byrevolving e- around the nucleus.
The distance of the orbit from thenucleus for a given e- is fixed.
Orbit has 2D representation.
Orbits are circular in shape.
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Orbital
Orbital is a region of space around thenucleus of the atom where an e- is most
likely to be found. It is impossible to know the exact position of
an e- in an orbital of an atom.
Orbital has 3D representation.
Orbital have different shapes like sphere,dumb-bell etc.
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Modern Periodic Table
The modern periodic table consists ofhorizontal rows called periods and
vertical columns called groups.
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Periods
There are 7 periods. First three are calledshort period. The fourth and fifth period iscalled long periods. The sixth period is calledvery long period. The seventh period isincomplete.
General characteristics of periods: -
Same number of shells of electrons. Period ends with inert gas.
Gradual change in property.
Change in valency.
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Groups
There are 9 groups from 0 to VIII group. The0 group contains inert gases. In the longperiods, the group I to VII are further sub-divided into A and B families.
General characteristics of groups: -
Valences are same.
Similarity in properties. Gradual Change in properties in some
elements.
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Chemical Bonding
When two atoms tend to remaintogether than separate from each
other, they are said to be in chemicalbonding with each other.
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Electronic Theory of Valency
According to electronic theory ofvalency, the valency of an element
depends on the number of electronpresent in the outermost orbit of theatom of the element known as valance
electron.
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Types of Bonds
Ionic Bond
Covalent Bond
Co-Ordinate Covalent Bond
Metallic Bond
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Ionic Bond
Ionic bonds are made by the transfer of theelectron from one atom to another.
Example: - The atomic number of Sodium (Na) is11. So its electronic configuration is 1s2 2s2 2p63s1. Also the atomic number Chlorine (Cl) is 17.So its electronic configuration is 1s2 2s2 2p6 3s23p5.
The Na atom loses one electron to the Cl atom.In doing so Na atom acquires a unit positivecharge while Cl atom acquires a unit of negativecharge. These two oppositely charged atomsattracts each other and forms an Ionic Bond as
NaCl.
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Ionic Compound
Ionic compounds are made by thetransfer of the electron from one atom
to another. They conduct electricity in a fused
state.
They show isomerism. They are usually liquids o gases in room
temperature.
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Covalent Bond
Covalent bonds are made by mutualsharing of electrons.
Example: - Oxygen atom has 6electrons in its outer most orbit. In theformation of Oxygen 2 atoms of Oxygen
contributes one electron each forsharing and thus acquire a stableconfiguration as O2.
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Covalent Compound
Covalent compounds are made bymutual sharing of electrons.
They doesnt conduct electricity.
They dont show isomerism.
They are usually solids.