Although both br3- and i3- ions are known, the f3- ion has not been observed. explain.

Fluorine, iodine and bromine are all in the same group. Fluorine been the first element in the group has less number of electron orbitals compare with bromine and iodine. Bromine and iodine has D orbitals which can take part in their bonding activities, this allows the elements to bond in a variety of ways, but fluorine does not have the D orbital and therefore is limited in its ion formation. 

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