Saturday, February 18, 2017

stability - Why do compounds form if overall energy of free ion increases according to CFT


According to crystal field theory, a free ion has certain energy and its energy increases when it is symmetrically surrounded by ligands. Now the degenerate d orbitals split into two new set of degenerate orbital, (eg and t2g) of which t2g has lower energy than symmetrically surrounded ion (the Bari centre) but still the energy of t2g is greater than the energy of the FREE ion according to diagram. (And energy of eg is much greater than free ion and Bari centre)



the energy level diagram


Now, my question is, if the energy of the overall ion afterwards is greater than the energy of the free ion, then why are coordinate compounds considered more stable than the free ion?( according to books) Or why do they form?




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periodic trends - Comparing radii in lithium, beryllium, magnesium, aluminium and sodium ions

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