How can you tell when a compound will form a covalent bond or a coordinate bond? I know that a coordinate bond is a special type of covalent bond and if during covalent bonding, if the elements taking part do not obtain a noble gas configuration, they for coordinate bonds. But take for example, boron trifluoride. Why does this not form a coordinate bond? Boron is electron deficient and has not obtained a noble gas configuration, shouldn'y it form a coordinate bond with fluorine?