Distribution of
Electron – Bohr’s & Bury Principle
Bohr & Bury stated certain principles for the
electron distribution in the shells. According to them, electrons revolve around
the nucleus in fixed orbits. These orbits can consist of a fixed number of
electrons which follow the following rules:
(i) The
maximum number of electrons which can be accommodated by an orbit is 2n2.
First orbit – K
Shell = 2 x 12 = 2 electrons (n = 1)
Second orbit – L
Shell = 2 x 22 = 8 electrons (n = 2)
Third orbit – M
Shell = 2 x 32 = 18 electrons (n = 3)
Forth orbit – N
Shell = 2 x 42 = 32 electrons (n = 4)
( (ii)
The valence shell (outer most
shell) cannot consist of more than 8 electrons.
( (iii) If
valence shell requires to fill more than 8 electrons then a new shell is
started which can contain maximum 2 electrons until previous shell is filled according
to its capacity.
(i (iv) The
penultimate (Last second) shell cannot consist of more than 18 electrons.
Atomic Number (Z)
|
Name and symbol of element
|
Electronic Distribution in various shells
|
Electronic configuration (In shell notation)
|
|||
(n = 1)
K
|
(n = 2)
L
|
(n = 3)
M
|
(n = 4)
M
|
|||
1
|
Hydrogen (H)
|
1
|
1
|
|||
2
|
Helium (He)
|
2
|
2
|
|||
3
|
Lithium (Li)
|
2
|
1
|
2, 1
|
||
4
|
Beryllium (Be)
|
2
|
2
|
2, 2
|
||
5
|
Boron (B)
|
2
|
3
|
2, 3
|
||
6
|
Carbon (C)
|
2
|
4
|
2, 4
|
||
7
|
Nitrogen (N)
|
2
|
5
|
2, 5
|
||
8
|
Oxygen (O)
|
2
|
6
|
2, 6
|
||
9
|
Flourine (F)
|
2
|
7
|
2, 7
|
||
10
|
Neon (Ne)
|
2
|
8
|
2, 8
|
||
11
|
Sodium (Na)
|
2
|
8
|
1
|
2, 8, 1
|
|
12
|
Magnesium (Mg)
|
2
|
8
|
2
|
2, 8, 2
|
|
13
|
Aluminium (Al)
|
2
|
8
|
3
|
2, 8, 3
|
|
14
|
Silicon (Si)
|
2
|
8
|
4
|
2, 8, 4
|
|
15
|
Phosphorus (P)
|
2
|
8
|
5
|
2, 8, 5
|
|
16
|
Sulphur (S)
|
2
|
8
|
6
|
2, 8, 6
|
|
17
|
Chlorine (Cl)
|
2
|
8
|
7
|
2, 8, 7
|
|
18
|
Argon (Ar)
|
2
|
8
|
8
|
2, 8, 8
|
|
19
|
Potassium (K)
|
2
|
8
|
8
|
1
|
2, 8, 8, 1
|
20
|
Calcium (Ca)
|
2
|
8
|
8
|
2
|
2, 8, 8, 2
|