Explain the rule with example according to which electrons are filled in various energy levels.
Explain the rule with example according to which electrons are filled in various energy levels.
The atom is built up by filling electrons in various orbitals according to the following rules.
Aufbau Principle:
This principle states that the electrons are added one by one to the various orbitals in order of their increasing energy starting with the orbital of lowest energy.
The increasing order of energy of various orbital is
1s , 2s , 2p , 3s , 3p , 4s , 3d , 4p , 5s , 4d , 5p , 6s , 4f , 5d , 6p , 5f , 6d , 7p ………..
How to remember such a big sequence? To make it simple we are giving you the method to write the increasing order of the orbitals.
Starting from the top, the direction of the arrows gives the order of filling of orbitals.
Alternatively, the order of increasing energies of the various orbitals can be calculated on the basis of (n+l) rule.
The energy of an orbital depends upon the sum of values of the principal quantum number (n) and the azimuthal quantum number (l). This is called (n + l) rule .
According to this rule,
” In neutral isolated atom, the lower the value of (n+ l) for an orbital, lower is its energy.
However, if the two different types of orbitals have the same value of (n+ l), the orbitals with lower value of n has lower energy “.
PAULI’S EXCLUSION PRINCIPLE :
According to this principle, an orbital can contain a maximum number of two electrons and these two electrons must be of opposite spin.
HUND’S RULE OF MAXIMUM MULTIPLICITY :
This rule deals with the filling of electrons in the equal energy (degenerate) orbitals of the same sub shell (p , d and f ). According to this rule ,
” Electron pairing in p ,d and f orbitals cannot occur untill each orbital of a given subshell contains one electron each or is singly occupied “.
This is due to the fact that electrons being identical in charge, repel each other when present in the same orbital.
This repulsion can, however, be minimised if two electrons move as far apart as possible by occupying different degenerate orbitals.
All the electrons in a degenerate set of orbitals will have same spin.
The atom is built up by filling electrons in various orbitals according to the following rules.
Aufbau Principle:
This principle states that the electrons are added one by one to the various orbitals in order of their increasing energy starting with the orbital of lowest energy.
The increasing order of energy of various orbital is
1s , 2s , 2p , 3s , 3p , 4s , 3d , 4p , 5s , 4d , 5p , 6s , 4f , 5d , 6p , 5f , 6d , 7p ………..
How to remember such a big sequence? To make it simple we are giving you the method to write the increasing order of the orbitals.
Starting from the top, the direction of the arrows gives the order of filling of orbitals.
Alternatively, the order of increasing energies of the various orbitals can be calculated on the basis of (n+l) rule.
The energy of an orbital depends upon the sum of values of the principal quantum number (n) and the azimuthal quantum number (l). This is called (n + l) rule .
According to this rule,
” In neutral isolated atom, the lower the value of (n+ l) for an orbital, lower is its energy.
However, if the two different types of orbitals have the same value of (n+ l), the orbitals with lower value of n has lower energy “.
PAULI’S EXCLUSION PRINCIPLE :According to this principle, an orbital can contain a maximum number of two electrons and these two electrons must be of opposite spin.
HUND’S RULE OF MAXIMUM MULTIPLICITY :This rule deals with the filling of electrons in the equal energy (degenerate) orbitals of the same sub shell (p , d and f ). According to this rule ,
” Electron pairing in p ,d and f orbitals cannot occur untill each orbital of a given subshell contains one electron each or is singly occupied “.
This is due to the fact that electrons being identical in charge, repel each other when present in the same orbital.
This repulsion can, however, be minimised if two electrons move as far apart as possible by occupying different degenerate orbitals.
All the electrons in a degenerate set of orbitals will have same spin.
