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Syllabus JEE MAINS
ATOMIC STRUCTURE Thomson and Rutherford atomic models and their limitations;
Nature of electromagnetic radiation, photoelectric effect; Spectrum of hydrogen atom, Bohr
model of hydrogen atom - its postulates, derivation of the relations for energy of the electron
and radii of the different orbits, limitations of Bohr‟s model; Dual nature of matter, deBroglie‟s relationship, Heisenberg uncertainty principle
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Quick Revision Notes
1
...
000546

1
...
00899

kg

9
...
673 × 10–27

1
...
602 × 10–19

+1
...
8 × 10–10

+4
...
76 × 108

9
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PLANCK'S QUANT UM THEORY
Electromagnetic radiation travels in the form of energy packets called as quantum
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The energy of one quantum (or Photon) E
= frequency of the radiation
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62× 10 -34 Joules sec
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3
...

The electrons in an atom revolve around the nucleus in certain discrete orbits
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The force of attraction between the nucleus and the electron is equal to centrifugal force
of the moving electron
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i
...
,

mvr

n

h
2

Where, m = mass of the electron, r = radius of the electronic orbit, v = velocity of the electron
in its orbit
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The emitted or absorbed energy

E is given by

E =h

The lowest energy state (n=1) is called the ground state
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It has to fall back to a lower orbit with
the release of energy
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g
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Radius of Bohr’s orbit

rn =

n2
× 0
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188× 10 6 m
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E
...
E
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6×

kZe 2
2r
kZe 2
r

Z2
ev/atom
n2

or

E T = -1312×

Z2
KJ/mol
n2

When an electron jumps from an outer orbit (higher energy) n 2 to an inner orbit (lower
energy) n1 , it emits energy in the form of electromagnetic radiations whose wavelength is
calculated by Rydberg’s Equation
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= RZ2

1 1
2
n1 n 2
2

where, R=Rydberg constant 109678cm 1
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The emission spectrum of hydrogen is divided in to six series
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

First line of a series: It is called line of longest wavelength or line of shortest
energy
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min =

2
n1
R

When electron returns from n2 to n1, the number of lines in the spectrum will be
equal to
5
...
Thus an electron, behaves both as a material particle and as a wave
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h
,
mv

6
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According to uncertainty principle “It is impossible to specify at any given moment both
the position and momentum (or velocity) of an electron”
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p

h
4

Where x uncertainty in position
m = mass of particle
7
...
1

x
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(b)
The energy of the electron
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2

(c)
The maximum number of electron in an orbit (by 2n 2
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(b)
The shape of subshells
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h
2π

l(l+ 1)

(d)
(e)

7
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For a given value of „n‟ the total value of „l‟ is always equal to the value of „n‟
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The electron enters in that sub orbit whose (n + l) value or the value of energy is less
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It tells about the splitting of spectral lines in the magnetic field i
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this quantum number
proved the Zeeman effect
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For a given value of „n‟ the total value of ‟m‟ is equal to n2
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7
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The value of s is 1/2 and -1/2 , which is signifies the spin or rotation or direction of
electron on it‟s axis during movement, may be in clockwise or anticlockwise
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NODES
 The region around the nucleus where density of electron cloud is zero (i
...
Ψ 2 = 0) is
known as node
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 Nodes are of two types (1) Angular nodes (2) Radial nodes
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of Angular nodes = 
The no
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of nodes in an orbital = n - 1

8
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Filling up of orbitals in the ground state of atom is governed by the following rules:

(1)

Aufbau principle: According to this principle, “In the ground state, the atomic orbitals
are filled in order of increasing energies i
...
in the ground state the electrons first occupy
the lowest energy orbitals available”
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Lower the value of
n + l, lower is the energy of the orbital and such an orbital will be filled up first
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Thus, order of filling up of orbitals is as follows:

1s< 2s< 2p< 3s< 3p< 4s< 4p< 5s< 4d< 5p< 6s< 6f< 5d

(2)

Pauli’s exclusion principle: “No two electrons in an atom can have same set of all the
four quantum numbers n, l, m and s
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(3)

Hund’s Rule of maximum multiplicity: “Electron filling will not take place in orbitals of
same energy until all the available orbitals of a given subshell contain one electron each
with parallel spin”
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John Dalton 1808, believed that matter is made up of extremely minute indivisible particles,
called atom which can takes part in chemical reactions
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However, modern researches have conclusively proved that atom is no longer an
indivisible particle
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