Electronic Configuration of Atoms.
It is the distribution or representation of electrons into different shells, subshells and orbitals of an atom.
On the basis of the formula i.e 2n²
where n is the principle shell, we can write electronic configuration of atoms in shells i.e K, L, M, N ...
1st shell K contains 2 electrons as n=1 , 2n¹=2 х 1²=2.
2nd shell L contains 8 electrons as n=2, 2n²=2 x 2² = 8
3rd shell M contains 18 electrons as n=3, 2n³=2 x 3² = 18
and so on.
The order of electronic configuration becomes 2, 8, 18, 32...
But for orbitals s, p, d, f... we should have a little bit knowledge of some rules i.e Aufbau principle, Pauli's Exclusion Principle and Hund's rule of maximum multiplicity. etc
the electronic configuration of any orbital can be simply represented as
nlˣ
n= number of the principle shell
l= subshell or orbital
x= number of electrons in that orbital.
Aufbau Principle states that orbitals are successively filled in order of their increasing energy, lowest energy orbital being filled first . Order of filling orbitals is shown as in figure, following the arrows.
the sequence of orbitals on the basis of increasing energy becomes as
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s...
where s orbital contains 2 electrons
p orbital contains 6 electrons
d orbital contains 10 electrons
f orbital contains 14 electrons
It is the distribution or representation of electrons into different shells, subshells and orbitals of an atom.
On the basis of the formula i.e 2n²
where n is the principle shell, we can write electronic configuration of atoms in shells i.e K, L, M, N ...
1st shell K contains 2 electrons as n=1 , 2n¹=2 х 1²=2.
2nd shell L contains 8 electrons as n=2, 2n²=2 x 2² = 8
3rd shell M contains 18 electrons as n=3, 2n³=2 x 3² = 18
and so on.
The order of electronic configuration becomes 2, 8, 18, 32...
But for orbitals s, p, d, f... we should have a little bit knowledge of some rules i.e Aufbau principle, Pauli's Exclusion Principle and Hund's rule of maximum multiplicity. etc
the electronic configuration of any orbital can be simply represented as
nlˣ
n= number of the principle shell
l= subshell or orbital
x= number of electrons in that orbital.
Aufbau Principle states that orbitals are successively filled in order of their increasing energy, lowest energy orbital being filled first . Order of filling orbitals is shown as in figure, following the arrows.
the sequence of orbitals on the basis of increasing energy becomes as
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s...
where s orbital contains 2 electrons
p orbital contains 6 electrons
d orbital contains 10 electrons
f orbital contains 14 electrons
EXAMPLES
for Hydrogen atom (Z=1)
electronic configuration is 1s¹
Helium atom (Z=2)
electronic configuration 1s²
Sodium (Z=11)
electronic configuration is 1s², 2s², 2p⁶, 3s¹
this is the full electronic configuration.
If we want to write only outer electronic configuration we have to remember the electronic configuration or atomic numbers of Noble gases .
For example
Full configuration of carbon(Z=6) is
1s² 2s² 2p²
outer electronic configuration is
[He]² 2s² 2p²
[He]² denotes 1s²
just remember that writing the outer configuration of any element we should write first that Noble gas in square brackets that lies one period before the given element in the periodic table. In the above example we write Helium as it is one period before carbon.
similarly for Chlorine (Z=17)
the full configuration is 1s² 2s² 2p⁶ 3s² 3p⁵
[Ne]¹⁰ 3s² 3p⁵
[Ne]¹⁰ denotes 1s² 2s² 2p⁶
Neon lies one period before Chlorine in the periodic table.
Electronic configuration for all elements is given in the figures.
Note that we cannot write electronic configuration for all elements on the basis of Aufbau principle due to various reasons as mentioned below.
Limitations of Aufbau principle
1. Electronic configuration of atoms involving ns and (n-1)d subshells.
2. Electronic configuration of Lanthanides and Actinides
3. Electronic configuration of ions.
4. Electronic configuration of 2nd and 3rd transition series.
for explanation visit other posts.
electronic configuration is 1s¹
Helium atom (Z=2)
electronic configuration 1s²
Sodium (Z=11)
electronic configuration is 1s², 2s², 2p⁶, 3s¹
this is the full electronic configuration.
If we want to write only outer electronic configuration we have to remember the electronic configuration or atomic numbers of Noble gases .
For example
Full configuration of carbon(Z=6) is
1s² 2s² 2p²
outer electronic configuration is
[He]² 2s² 2p²
[He]² denotes 1s²
just remember that writing the outer configuration of any element we should write first that Noble gas in square brackets that lies one period before the given element in the periodic table. In the above example we write Helium as it is one period before carbon.
similarly for Chlorine (Z=17)
the full configuration is 1s² 2s² 2p⁶ 3s² 3p⁵
[Ne]¹⁰ 3s² 3p⁵
[Ne]¹⁰ denotes 1s² 2s² 2p⁶
Neon lies one period before Chlorine in the periodic table.
Electronic configuration for all elements is given in the figures.
Note that we cannot write electronic configuration for all elements on the basis of Aufbau principle due to various reasons as mentioned below.
Limitations of Aufbau principle
1. Electronic configuration of atoms involving ns and (n-1)d subshells.
2. Electronic configuration of Lanthanides and Actinides
3. Electronic configuration of ions.
4. Electronic configuration of 2nd and 3rd transition series.
for explanation visit other posts.
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