My textbook says despite large electronegativity difference it's covalent since beryllium ion will have too much charge density and it'll attract fluorine election cloud and therfore forms polar covalent bound.
But I looked it up in Wikipedia and found out that it has a crystal lattice, is Soluble in water and has a quiet high melting point.
What else one needs to call a compound ionic? Am I or the textbook right?
Thanks for your help!