Question :

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

Subject

Science

Standard

Class 9

Views

1166

Asked By

Mukesh

Seema
Answer / Solution

The rules for writing of distribution of electrons in various shells for the first eighteen elements are:

The maximum number of electrons present in a shell is given by the formula is 2n2.

We take, the orbit number n i.e., n = 1, n = 2, and n = 3 for calculation. Now, Maximum number of electrons in different shells are:

  1. K shell n = 1 ⇒ Maximum number if electrons are 2n2 ⇒ 2(1)2 = 2
  2. L shell n = 2 ⇒ Maximum number if electrons are 2n2 ⇒ 2(2)2 = 8
  3. M shell n = 3 ⇒ Maximum number if electrons are 2n2 ⇒ 2(3)2 = 18
  4. N shell n = 4 ⇒ Maximum number if electrons are 2n2 ⇒ 2(4)2 = 32
Aanya
Answer / Solution

The maximum number of electrons present in a shell is given by the formula is 2n2.

For K shell (n = 1) ⇒ 2n2 = 2(1)2 = 2, L shell (n = 2)  ⇒ 2n2 = 2(2)2 = 8, M shell (n = 3) ⇒ 2n2 = 2(3)2 = 18, N shell (n = 4) ⇒ 2n2 = 2(4)2 = 32. 

Knowledge
Answer / Solution

The distribution of electrons in different orbits or shells is governed by a scheme known as Bohr bury scheme.The arrangement of electrons in various energy levels of an atom is known as the electronic configuration of the atom. According to this scheme.

  1. The electrons are arranged around the nucleus in different energy levels or energy shells. The electrons first occupy the shell with the lowest energy i.e., closest to the nucleus.
  2. The first or the innermost energy shell (K or n = 1) can take only two electrons.
  3. The second shell (L or n = 2) can contain upto 8 electrons.
  4. From third shell (M or n = 3) onwards, the shells become bigger. The third shell can accommodate as many as 18 electrons. In general, the maximum number of electrons that can be present in any shell is 2n2 where n is the number of energy shell. Thus, the first orbit (n = 1, known as K shell) can contain 2 × 12 = 2 electrons, the second orbit (n = 2, known as L shell) can contain 2 × 22 = 8 electrons.

Maximum No. of electrons in different orbits

 

Orbit

Value of n Maximum no. of electrons in the orbit

K

1 2 × 12 = 2
L 2

2 × 22 = 8

M

3 2 × 32 = 18
N 4

2 × 42 = 32

The outermost shell of an atom cannot have more than 8 electrons and the shell next to the outermost shell cannot have more than 18 electrons.


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