Question

Explain Hund' s rule of maximum multiplicity by taking eg. of nitrogen

Answer 1

Hund's rule of maximum multiplicity states that if two or more orbitals of same energy are available, electrons first fill the available orbitals singly and then proceeds to fill them in pairs.

Examples:

Carbon: Its electronic configuration is 1s2 2s2and 2p2

In, p there are three orbitals of equal energies. So, the electrons will first fill them singly. So, two orbitals have one electron each instead of one orbital having 2 electrons.

Fluorine: Its electronic configuration is 1s2 2s2and 2p5

In, p there are three orbitals of equal energies. So, the electrons will first fill them singly. So, three orbitals get filled by one electron and then they are filled in pairs. So, two orbitals have paired electrons and one orbital has a singly filled orbital.

Answer 2

Hund's rule of maximum multiplicity is a rule based on observation of atomic spectra, which is used to predict the ground state of an atom or molecule with one or more open electronic shells. The rule states that for a given electron configuration, the lowest energy term is the one with the greatest value of spin multiplicity.[1] This implies that if two or more orbitals of equal energy are available, electrons will occupy them singly before filling them in pairs. The rule, discovered by Friedrich Hund in 1925, is of important use in atomic chemistry, spectroscopy, and quantum chemistry, and is often abbreviated to Hund's rule, ignoring Hund's other two rules.
see example,


e.g. Nitrogen has seven atomic number means seven electron. 
electronic configuration is given as. 
N(7)- 1s^2 2s^2 2px^1 2py^1 2pz^1 
clearly p orbital of Nitrogen having 1 electron in it.