**STABILITY – ORBITALS**

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**STABILITY – ORBITALS**

The stability of half filled orbitals ( p^{3}, d^{5}, f^{7 }) and full filled orbitals ( p^{6}, d^{10}, f^{14 }) depends upon the symmetrical distribution of charge, symmetrical distribution of charge decreases the energy of the system & hence its stability is increased. To understand the effect of the symmetrical distribution of charge in orbitals, we consider the shapes of orbitals.

The s-orbital is spherical in shape & hence the electronic charge would be distributed uniformly in all directions.

In the three p-orbitals, px, py & pz are symmetrical along. x , y & z axis respectively. In px’, the electronic charge would be concentrated along *x-*axis, Similarly in py & pz configuration, the electronic charge would be mainly concentrated along ‘y’ & ‘z’ axis respectively. In px^{2} py’ pz’ configuration the electronic charge would be more concentrated along x-axis. In px^{2} , py^{2}, pz^{1} configuration, the electronic change would be more in plane xy . So in all these p-configurations, the distribution of charge is unsymmetrical.

The distribution of charge in px^{1 }py^{1 }pz^{1 } & px^{2 }py^{2 }pz^{2 } configuration would be symmetrical in all directions. So symmetrical configuration of change decreases the energy & hence higher stability.

Similarly the configuration of *d-*obitals d^{5} & d^{10} have symmetrical distribution of charge.

half filled orbitals Full filled d-orgitals

So these configuration would be more stable than other *d-*configurations.

Therefore half filled & full filled orbitals are more stable than other electronic configuration.

For Ex.

_{24}Cr– 1s^{2}, 2s^{2}, 3s^{2}, 3p^{6}, 4s^{2}, 3d^{4 }(expected)

_{ 24}Cr – 1s^{2}, 2s^{2}, 2p^{6}, 3s^{2}, 3p^{6}, 4s^{1}, 3d^{5} (Correct)

_{ 29}Cu– 1s^{2}, 2s^{2}, 2p^{6}, 3s^{2}, 3p^{6}, 4s^{1}, 3d^{9} (expected )

_{ 29}Cu– 1s^{2}, 2s^{2}, 2p^{6}, 3s^{2}, 3p^{6}, 4s^{1}, 3d^{10 }(correct)

Half filled & full filled orbitals have lower energy & hence higher stability, therefore , to acquire extra stability one electron from 4s orbital goes into 3d orbital which become half filled or full filled.