Friday, 5 January 2018

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Answer : The following rules are followed for writing the distribution of electrons in different energy
levels or shells for the first eighteen elements :
(i) The maximum number of electrons present in a shell is given by the formula 2n2, where 'n' is the orbit
number or energy level index, 1,2,3,….Hence the maximum number of electrons in different shells are as
follows:
first orbit or K-shell will be = 2 × 12 = 2,
second orbit or L-shell will be = 2 × 2= 8,
third orbit or M-shell will be = 2 × 32= 18,
fourth orbit or N-shell will be = 2 × 42= 32,
(ii) The maximum number of electrons that can be accommodated in the outermost orbit is 8.
(iii) Electrons are not accommodated in a given shell, unless the inner shells are filled. That is, the shells are filled in a step-wise manner.

Distribution of electrons in various shells for the first eighteen elements
ElementSymbolAtomic NumberNumber of Electron
Distribution of electrons
KLMN
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminium
Silicon
Phosphorus
Sulphur
Chlorine
Argon
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
A
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
-
-
1
2
3
4
5
6
7
8
8
8
8
8
8
8
8
8
-
-
-
-
-
-
-
-
-
-
1
2
3
4
5
6
7
8
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-

This is an answered question from Chapter 4. Structure Of The Atom of CBSE Class 9th Science

Check for Complete Exercise Solution for Chapter 4. Structure Of The Atom | CBSE Class 9th Science

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