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Objectives:
1) Define the orbital
2) Describe all the 4 quantum numbers ofan electron in an orbital:
i. principal quantum number, n
ii. Angular momentum quantum number, l
iii. Magnetic quantum number, m
iv. Electron spin quantum number, s
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AtomicOrbital
An orbital is a three-dimensional region inspace around the nucleus
where there is a highprobability of finding anelectron.
Definition
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QUANTUM NUMBER
Each of the electrons in an atom isdescribed and characterised by a setof four quantum numbers, namely
a) principal quantum number, n
b) angular momentum quantum number, l
c) magnetic quantum number, m
d) electron spin quantum number, s.
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Principle Quantum Number(n )
n= 1, 2, 3, 4, ,
2.2
Indicates the energy level of aspecific electron also known shell
The
principal quantum number mayhave only integral values:
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Angular Momentum Quantum Number, l
Letters are assigned to different numerical values ofl.
Numericalvalue ofl Symbol
0
1
2
3
Orbital shape
s
p
d
f
spherical
dumbbell
cloverleaf
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Angular Momentum Quantum Number, l
- lis dependant on n. (i.e., 0 l< n).Value of n Value ofl Subshells
1 0 1s
2 0,1 2s, 2p
3 0,1,2 3s,3p,3d
4 0,1,2,3 4s,4p,4d,4f
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l= 2 (d orbitals)
l= 0 (s orbital) l= 1 (p orbital)
l= 2 (d orbitals)l= 2 (d orbital)
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for a given value of l
m= -l,., 0, . +l
~is orientation of the orbital in space
ifl= 1 (p orbital), m = -1, 0, or1
ifl= 2 (d orbital), m= -2, -1, 0, 1, or2
Magnetic Quantum Numberm
2.2
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Exercise
Shell nl
(l
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Electron Spin Quantum Number, s
The value ofs determines the direction of spinningmotions of an electron (either clockwise or counterclockwise) which is spinning on its own axes, as Earthdoes.
The electron spin quantum number has a value of+
1
2-
1
2or
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PrincipleQuantumNumber,
n (shell)
AngularMomentum(subshell)
Subshelldsgntn
MegneticQuantumNumber, l
Electronspin
quantumnumber,
s
No. oforbitals
in
subshell
Numberof
electron
1 0 1s 0 1 2
20 2s 0 1
81 2p -1, 0, +1 3
3
0 3s 0 1
181 3p -1, 0, +1 3
2 3d-2, -1, 0, +1,
2 5
4
0 4s 0 1
32
1 4p -1, 0, +1 3
2 4d-2, -1, 0, +1,
2 5
3 4f-3, -2, -1, 0,
+1, 2, 3 7
n 2n2
Table 1: The four quantum numbers of electron.