In my textbook its mentioned that BeCO3 (beryllium carbonate) is an ionic compound, but going according to fajans rules, small cation with high charge density and large anion should give a majorly covalent compound.

  • 1
    $\begingroup$ Relatively small, electronegative oxygen atoms in large anions are less polarizable than big single-atom anions like iodide. $\endgroup$
    – Poutnik
    Mar 12 at 6:39
  • $\begingroup$ Beryllium carbonate is unstable. Mismatch is size is too large, and carbonate have a general tendency to break down to CO2 and oxides. $\endgroup$
    – Mithoron
    Mar 12 at 13:31
  • $\begingroup$ For delocalized electrons, it does provide some insight. However, strictly speaking, Fajan rule is only applicable to atoms and ions. Hard-Soft Acid-Base theory is more widely applicable for polyatomic ions. $\endgroup$
    – ananta
    Mar 12 at 18:58


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.