Chemistry Series Chapter 2: Structure Of Atom | Part - 3 | Orbits And Energy Levels

Neutrons :

J. Chadwick discovered another subatomic particle that had no charge and a mass which was nearly equal to that of a proton. 
It was discovered in 1932.
It has been found that neutrons are present in the nucleus of all the atoms, except hydrogen.
It is represented as 'n'.
Electrons – they carry a negative charge.
Protons – they carry a positive charge.
Neutrons – they carry no charge, they are neutral.

Distribution of Electrons in Different Orbits or Cells :
    1]The arrangement of electrons in various shells that is energy levels of an atom of the element is known as its electronic configuration.
    2]The distribution of electrons into different orbits or shells of an atom was suggested by Bohr and Bury.


The rules for writing the number of electrons in different energy levels or shells are as follows :
    1]The maximum number of atoms that can fit in energy levels or shells can be found by 2n2 where ‘n’ stands for 1, 2, 3, 4 .... ( that is used for K, L, M, N,,, and so on ).
    2]The maximum number of electrons in their outermost shell or orbit can be 8.
    3]If the inner shell is filled then only electrons can be accommodated in given shells.
    For example- if shell ‘K’ will be filled with electrons then only shell ‘L’ will accommodate.
    The shells are filled in a stepwise manner.

Orbit :
It can be defined as the circular path around the nucleus. 
It is also known as energy levels or shells. 
They are represented by K, L, M, N, and so on.
First orbit is denoted by K.
Second orbit is denoted by L.
Third orbit is denoted by M.
Fourth orbit is denoted by N.
Number of electrons in K shell :
      Here, n = 1Therefore = 2n2  = 2 × (1) 2  = 2
      Thus, the maximum number of electron in K shell is 2.

Number of electrons in L shell :
      Here, n = 2Therefore = 2n2  = 2 × (2) 2  = 2 × 4 = 8
      Thus, the maximum number of electron in L shell is 8.

Number of electrons in M shell :
      Here, n = 3Therefore = 2n2  = 2 × (3) 2  = 2 × 9 = 18
      Thus, the maximum number of electron in M shell is 18.

In the same way, we can find the number of electrons for the N shell.