max covalency ???

I have read somewhere.. the maximum covalecy that an atom can show is the total no. of orbitals it has. Weather filled or unfilled...

And so in case of Boron its 1 + 3 = 4

how can we find the max. covalency of an element like Gallium..??? etc.. maybe its a silly question.. but i m too poor in inorganic chem...!!

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