Structure of Atom Class 11 Notes Chemistry Chapter 2

 Page 1


• Information about fundamnetal particles of atom
Name of  UNIT Electron Proton Neutron
Constant 
Mass amu 0.000546 1.00728 1.008665
kg 9.109 × 10
–31
1.673 × 10
–27
1.675 × 10
–27
Charge Coloumbs – 1.602 × 10
–19
+ 1.602 × 10
–19
Zero
esu – 4.8 × 10
–10
+ 4.8 × 10
–10
Zero
Relative – 1 + 1 Zero
• Electromagnetic radiations : Energy emitted from any source (in forms
of waves) in which electric and magnetic fields oscillated perpendicular to
each other and travelling with a velocity of light is known as EM radiation.
• Characteristics of waves :
(a) Wavelength : The distance of one crest and
one trough in a wave. Denoted by ‘ ?’.
(b) Frequency : Number of waves passing 
through a given point in one second. 
 Denoted by ?. 
(c) Amplitude : The height of crest or depth of a trough denoted by ‘a’.
(d) Wave Number : Number of waves per unit length denoted by   
=  (or m
–1
)
Page 2


• Information about fundamnetal particles of atom
Name of  UNIT Electron Proton Neutron
Constant 
Mass amu 0.000546 1.00728 1.008665
kg 9.109 × 10
–31
1.673 × 10
–27
1.675 × 10
–27
Charge Coloumbs – 1.602 × 10
–19
+ 1.602 × 10
–19
Zero
esu – 4.8 × 10
–10
+ 4.8 × 10
–10
Zero
Relative – 1 + 1 Zero
• Electromagnetic radiations : Energy emitted from any source (in forms
of waves) in which electric and magnetic fields oscillated perpendicular to
each other and travelling with a velocity of light is known as EM radiation.
• Characteristics of waves :
(a) Wavelength : The distance of one crest and
one trough in a wave. Denoted by ‘ ?’.
(b) Frequency : Number of waves passing 
through a given point in one second. 
 Denoted by ?. 
(c) Amplitude : The height of crest or depth of a trough denoted by ‘a’.
(d) Wave Number : Number of waves per unit length denoted by   
=  (or m
–1
)
(e) Velocity : Linear distance travelled by a wave in one second.
velocity of light c =  = 
?	 							? =
• Energywise order for EM radiation.
cosmic < ? rays < X rays < UV < VIBGYOR < IR < Microwaves < Radiowaves
        ????????????????????????
		? (Inc.)                 ? (Dec.)               Energy (Dec.)
• Photon : A packet or particle of light energy is knows as Photon.
• Planck’s quantum theory : The energy emitted or absorbed by a source
is discontinuous in form of small packet  of energy, called quantum.
Quantum of light is called photon.
  E a v
  E = hv (h = Planck's constant)
  E = nhv (h = 6.626×10
–34
 J sec)
  If ‘n’ photons are emitted E = nh? 
• Photo electric effect : The phenomenon of ejection of electrons from a
metal surface when a light of suitable frequency falls on metal surface.
h? – h ?
0
 =  mv
2
h?	? Energy of incident light on metal surface.
h?
0
	? Work function of metal.
mv
2 
= Kinetic energy by which e
–
  is emitted from metal surface.
• de Broglie equation : All material particles in motion also exhibit wave like
properties.
hh
mv p
?= =
Page 3


• Information about fundamnetal particles of atom
Name of  UNIT Electron Proton Neutron
Constant 
Mass amu 0.000546 1.00728 1.008665
kg 9.109 × 10
–31
1.673 × 10
–27
1.675 × 10
–27
Charge Coloumbs – 1.602 × 10
–19
+ 1.602 × 10
–19
Zero
esu – 4.8 × 10
–10
+ 4.8 × 10
–10
Zero
Relative – 1 + 1 Zero
• Electromagnetic radiations : Energy emitted from any source (in forms
of waves) in which electric and magnetic fields oscillated perpendicular to
each other and travelling with a velocity of light is known as EM radiation.
• Characteristics of waves :
(a) Wavelength : The distance of one crest and
one trough in a wave. Denoted by ‘ ?’.
(b) Frequency : Number of waves passing 
through a given point in one second. 
 Denoted by ?. 
(c) Amplitude : The height of crest or depth of a trough denoted by ‘a’.
(d) Wave Number : Number of waves per unit length denoted by   
=  (or m
–1
)
(e) Velocity : Linear distance travelled by a wave in one second.
velocity of light c =  = 
?	 							? =
• Energywise order for EM radiation.
cosmic < ? rays < X rays < UV < VIBGYOR < IR < Microwaves < Radiowaves
        ????????????????????????
		? (Inc.)                 ? (Dec.)               Energy (Dec.)
• Photon : A packet or particle of light energy is knows as Photon.
• Planck’s quantum theory : The energy emitted or absorbed by a source
is discontinuous in form of small packet  of energy, called quantum.
Quantum of light is called photon.
  E a v
  E = hv (h = Planck's constant)
  E = nhv (h = 6.626×10
–34
 J sec)
  If ‘n’ photons are emitted E = nh? 
• Photo electric effect : The phenomenon of ejection of electrons from a
metal surface when a light of suitable frequency falls on metal surface.
h? – h ?
0
 =  mv
2
h?	? Energy of incident light on metal surface.
h?
0
	? Work function of metal.
mv
2 
= Kinetic energy by which e
–
  is emitted from metal surface.
• de Broglie equation : All material particles in motion also exhibit wave like
properties.
hh
mv p
?= =
For microscopic particles mass is very less therefore Wavelength of wave 
associated with it can be detected.
For macroscopic particles mass is large, ? of wave associated with it can 
not be detected. Hence dominant wave character.
Hence microscopic bodies have dual nature, where as macroscopic bodies 
have particle nature.
Heisenberg's Uncertainty Principle
It is impossible to determine the exact position and velocity of a moving 
subatomic particle simultaneously with accuracy.
?x × m ?v =	
?x = uncertainty in position
?v = uncertainty in velocity
Bohr’s theory for H [H like one e
–
 systems He
+
; Li
2+
]
(1) e
–
 revolving round the nucleus in circular path [stationary state; SHELL] 
with a definite angular momentum [n no. of shell of e
–
] and with 
definite  energy
 E
n
 =  ? – 2.18 × 10
–18
(2)  As n increases, Energy of e
–
 becomes less – ve [Due to less force of Proton 
attraction]
 As n decreases, Energy of e
–
 becomes More – ve [Due to more force of 
attraction by protons]
(3) In infinity shell e
–
 has zero force of attraction therefore zero energy.
Page 4


• Information about fundamnetal particles of atom
Name of  UNIT Electron Proton Neutron
Constant 
Mass amu 0.000546 1.00728 1.008665
kg 9.109 × 10
–31
1.673 × 10
–27
1.675 × 10
–27
Charge Coloumbs – 1.602 × 10
–19
+ 1.602 × 10
–19
Zero
esu – 4.8 × 10
–10
+ 4.8 × 10
–10
Zero
Relative – 1 + 1 Zero
• Electromagnetic radiations : Energy emitted from any source (in forms
of waves) in which electric and magnetic fields oscillated perpendicular to
each other and travelling with a velocity of light is known as EM radiation.
• Characteristics of waves :
(a) Wavelength : The distance of one crest and
one trough in a wave. Denoted by ‘ ?’.
(b) Frequency : Number of waves passing 
through a given point in one second. 
 Denoted by ?. 
(c) Amplitude : The height of crest or depth of a trough denoted by ‘a’.
(d) Wave Number : Number of waves per unit length denoted by   
=  (or m
–1
)
(e) Velocity : Linear distance travelled by a wave in one second.
velocity of light c =  = 
?	 							? =
• Energywise order for EM radiation.
cosmic < ? rays < X rays < UV < VIBGYOR < IR < Microwaves < Radiowaves
        ????????????????????????
		? (Inc.)                 ? (Dec.)               Energy (Dec.)
• Photon : A packet or particle of light energy is knows as Photon.
• Planck’s quantum theory : The energy emitted or absorbed by a source
is discontinuous in form of small packet  of energy, called quantum.
Quantum of light is called photon.
  E a v
  E = hv (h = Planck's constant)
  E = nhv (h = 6.626×10
–34
 J sec)
  If ‘n’ photons are emitted E = nh? 
• Photo electric effect : The phenomenon of ejection of electrons from a
metal surface when a light of suitable frequency falls on metal surface.
h? – h ?
0
 =  mv
2
h?	? Energy of incident light on metal surface.
h?
0
	? Work function of metal.
mv
2 
= Kinetic energy by which e
–
  is emitted from metal surface.
• de Broglie equation : All material particles in motion also exhibit wave like
properties.
hh
mv p
?= =
For microscopic particles mass is very less therefore Wavelength of wave 
associated with it can be detected.
For macroscopic particles mass is large, ? of wave associated with it can 
not be detected. Hence dominant wave character.
Hence microscopic bodies have dual nature, where as macroscopic bodies 
have particle nature.
Heisenberg's Uncertainty Principle
It is impossible to determine the exact position and velocity of a moving 
subatomic particle simultaneously with accuracy.
?x × m ?v =	
?x = uncertainty in position
?v = uncertainty in velocity
Bohr’s theory for H [H like one e
–
 systems He
+
; Li
2+
]
(1) e
–
 revolving round the nucleus in circular path [stationary state; SHELL] 
with a definite angular momentum [n no. of shell of e
–
] and with 
definite  energy
 E
n
 =  ? – 2.18 × 10
–18
(2)  As n increases, Energy of e
–
 becomes less – ve [Due to less force of Proton 
attraction]
 As n decreases, Energy of e
–
 becomes More – ve [Due to more force of 
attraction by protons]
(3) In infinity shell e
–
 has zero force of attraction therefore zero energy.
17
(4) Electron energy only changes by definite values ?E = E
f
  – E
i
.
Hydrogen spectrum : When e
–
 in hydrogen atom is provided energy it gets 
excited to higher shell from ground state, it comes back to ground state by 
emitting energy in definite values.
“Quanta” : The emission of light energy is known as emission spectra. It 
corresponds to each atom depending upon which energy shell e
– 
is excited. 
It is discontinuous spectra as ‘ ?’ of light radiations do not merge with each 
other like in VIBGYOR (Continous Spectra). 
 When e
–
 falls from any excited state to 
 = 1,09,678 R = Rydberg constant = 109678 cm
–1
n
i
  = 1, n
f
 = 2, 3, 4, .... [Lyman series] (UV)
n
i
  = 2, n
f
 = 3, 4, 5, .... [Balmer series] (VIBGYOR)
n
i
 = 3, n
f
 = 4, 5, 6 [Paschem series] IR.
n
i
 = 4, n
f
 = 5, 6, 7 [Bracket series] IR.
n
i
 = 5, n
f
 = 6, 7, 8 [Pfund series] IR.
Quantum numbers : The noumbers which completely define the state of 
e
–
 in an atom.
(1) Principal Quantum No. : It describes the distance of e
–
 from nucleus ‘n’ 
i.e., defines the shell no. It is denoted by ‘n’.
 n = 1, 2, 3, 4, 5, .....
   K, L, M, N, O .....
(2) Azimuthal (l) Quantum No. : It defines the path of e
–
 decided by angular 
momentum of e
–
. Each angular momentum value corresponds to one 
subshell. The no. of subshells in a shell is 0 to n – 1.
Page 5


• Information about fundamnetal particles of atom
Name of  UNIT Electron Proton Neutron
Constant 
Mass amu 0.000546 1.00728 1.008665
kg 9.109 × 10
–31
1.673 × 10
–27
1.675 × 10
–27
Charge Coloumbs – 1.602 × 10
–19
+ 1.602 × 10
–19
Zero
esu – 4.8 × 10
–10
+ 4.8 × 10
–10
Zero
Relative – 1 + 1 Zero
• Electromagnetic radiations : Energy emitted from any source (in forms
of waves) in which electric and magnetic fields oscillated perpendicular to
each other and travelling with a velocity of light is known as EM radiation.
• Characteristics of waves :
(a) Wavelength : The distance of one crest and
one trough in a wave. Denoted by ‘ ?’.
(b) Frequency : Number of waves passing 
through a given point in one second. 
 Denoted by ?. 
(c) Amplitude : The height of crest or depth of a trough denoted by ‘a’.
(d) Wave Number : Number of waves per unit length denoted by   
=  (or m
–1
)
(e) Velocity : Linear distance travelled by a wave in one second.
velocity of light c =  = 
?	 							? =
• Energywise order for EM radiation.
cosmic < ? rays < X rays < UV < VIBGYOR < IR < Microwaves < Radiowaves
        ????????????????????????
		? (Inc.)                 ? (Dec.)               Energy (Dec.)
• Photon : A packet or particle of light energy is knows as Photon.
• Planck’s quantum theory : The energy emitted or absorbed by a source
is discontinuous in form of small packet  of energy, called quantum.
Quantum of light is called photon.
  E a v
  E = hv (h = Planck's constant)
  E = nhv (h = 6.626×10
–34
 J sec)
  If ‘n’ photons are emitted E = nh? 
• Photo electric effect : The phenomenon of ejection of electrons from a
metal surface when a light of suitable frequency falls on metal surface.
h? – h ?
0
 =  mv
2
h?	? Energy of incident light on metal surface.
h?
0
	? Work function of metal.
mv
2 
= Kinetic energy by which e
–
  is emitted from metal surface.
• de Broglie equation : All material particles in motion also exhibit wave like
properties.
hh
mv p
?= =
For microscopic particles mass is very less therefore Wavelength of wave 
associated with it can be detected.
For macroscopic particles mass is large, ? of wave associated with it can 
not be detected. Hence dominant wave character.
Hence microscopic bodies have dual nature, where as macroscopic bodies 
have particle nature.
Heisenberg's Uncertainty Principle
It is impossible to determine the exact position and velocity of a moving 
subatomic particle simultaneously with accuracy.
?x × m ?v =	
?x = uncertainty in position
?v = uncertainty in velocity
Bohr’s theory for H [H like one e
–
 systems He
+
; Li
2+
]
(1) e
–
 revolving round the nucleus in circular path [stationary state; SHELL] 
with a definite angular momentum [n no. of shell of e
–
] and with 
definite  energy
 E
n
 =  ? – 2.18 × 10
–18
(2)  As n increases, Energy of e
–
 becomes less – ve [Due to less force of Proton 
attraction]
 As n decreases, Energy of e
–
 becomes More – ve [Due to more force of 
attraction by protons]
(3) In infinity shell e
–
 has zero force of attraction therefore zero energy.
17
(4) Electron energy only changes by definite values ?E = E
f
  – E
i
.
Hydrogen spectrum : When e
–
 in hydrogen atom is provided energy it gets 
excited to higher shell from ground state, it comes back to ground state by 
emitting energy in definite values.
“Quanta” : The emission of light energy is known as emission spectra. It 
corresponds to each atom depending upon which energy shell e
– 
is excited. 
It is discontinuous spectra as ‘ ?’ of light radiations do not merge with each 
other like in VIBGYOR (Continous Spectra). 
 When e
–
 falls from any excited state to 
 = 1,09,678 R = Rydberg constant = 109678 cm
–1
n
i
  = 1, n
f
 = 2, 3, 4, .... [Lyman series] (UV)
n
i
  = 2, n
f
 = 3, 4, 5, .... [Balmer series] (VIBGYOR)
n
i
 = 3, n
f
 = 4, 5, 6 [Paschem series] IR.
n
i
 = 4, n
f
 = 5, 6, 7 [Bracket series] IR.
n
i
 = 5, n
f
 = 6, 7, 8 [Pfund series] IR.
Quantum numbers : The noumbers which completely define the state of 
e
–
 in an atom.
(1) Principal Quantum No. : It describes the distance of e
–
 from nucleus ‘n’ 
i.e., defines the shell no. It is denoted by ‘n’.
 n = 1, 2, 3, 4, 5, .....
   K, L, M, N, O .....
(2) Azimuthal (l) Quantum No. : It defines the path of e
–
 decided by angular 
momentum of e
–
. Each angular momentum value corresponds to one 
subshell. The no. of subshells in a shell is 0 to n – 1.
18
 n   l (0 to n-1)
1  0 l = 0 ‘s’ subshell
2 0, 1 l = 1 ‘p’ subshell
3 0, 1, 2 l = 2 ‘d’ subshell
4, 0, 1, 2, 3 l = 3 ‘f ’ subshell
All subshells are wave functions for locating e
–
.
In the same shell energy increase s < p < d < f.
(3) Magnetic Quantum No. : It gives the no. of magnetic orientations 
an e
–
 can have in a subshell. That is number of orbitals in a sub-shell.  
m
s
 = –l........o........+ l = (2l + 1).
(4)  Spin Quantum No. : An e
–
 is continuously spinning on its own axis. 
The value of s = 
1
2
or –
1
2
An orbital can have maximum two e
–
 one with clockwise and other with 
anticlockwise spin.
Aufbau principle 
(a)  Electrons are filled in increasing order of energy of sub-shell. 
(b) As ‘n + l’value increases energy of e
–
 increases in that sub-shell.
(c)  For two sub-shells with same ‘n + l’ value, as ‘ n’ value increases  
 energy of e
–
 increases.
Pauli’s principle 
No two electrons can have same set of four quantum numbers in an atom. 
Hund’s rule of maximum multiplicity
The pairing of e
– 
in degenerate orbitals (different orbitals with same energy) 
will get paired only once they have been singly occupied with same spin.
Important Points
The filling of e
– 
in subshells follows this order. (As per Aufbau principle)
(A) 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p 
< 7s < 5f < 6d < 7p