Rules for filling electrons in various orbitals

Rules for filling electrons in various orbitals

1. Rules for filling electrons in
various orbitals
Dr. MithilFalDesai
Shree Mallikarjun and Shri Chetan Manju Desai College
Canacona Goa

2. Principal
quantum
number-n
Azimuthal quantum
number
0,….,(n-1)
1 0
2 0,1
3 0,1, 2
4 0,1,2,3
Azimuthal
quantum
number -l
Magnetic quantum
number m
l
(-l,..0..,+l)
Orbital
0 0 s
1 -1,0,+1 p
2 -2,-1,0,+1,+2 d
3 -3,-2,-1,0,+1,+2,+3f
Spin quantum
number -s
+½ or -½
Orbital Number of radial nodes
(n-l-1)
1s 1-0-1=0
2s 2-0-1=1
2p 2-1-1=0
3s 3-0-1=2
3p 3-1-1=1
3d 3-2-1=0
Stateofelectronisgiven
bysetoffourquantum
numbers.
(n,l,m
l,s)

3. Aufbau’s principle
Theelectronsareaddedoneby
onetothevariousorbitalsin
orderoftheirincreasingenergy
startingwiththeorbitalof
lowestenergy.Theincreasing
orderofenergyofvarious
orbitalsis
1s<2s<2p<3s<3p<4s<3d<3d<5s<
5p<6s<4f<5d<6p<7s<5f<6d<7p
1s
2s2p
3s3p3d
4s4p4d4f
5s5p5d5f
6s6p6d
7s7p

4. Pauli’s exclusion principle
No two electrons in an atom will have same value of all the four quantum
numbers.
If one electron in an atom has n = 1, l=0, m = 0, and s = +1/2, the quantum
numbers no other electron can have the same four quantum numbers.
n = 1, l=0, m
l= 0, and s = +1/2
n = 1, l=0, m
l= 0, and s = +1/2
1s
n = 1, l=0, m
l= 0, and s = +1/2
n = 1, l=0, m
l= 0, and s = -1/2
1s
n = 1, l=0, m
l= 0, and s = +1/2
n = 1, l=0, m
l= 0, and s = -1/2
1s
n = 1, l=0, m
l= 0, and s = +1/2

5. Hund’s Rule of maximum multiplicity
Electron pairing in p, d and f orbitals cannot occur until each orbitals of a given
subshell contains one electron each or is singly occupied.
2p
2p
x2p
y2p
z
2p
2p
x2p
y2p
z
3-electrons in p orbital
E
n
e
r
g
y