9701 · 3.4
Covalent bonding and coordinate (dative covalent) bonding — FAQ
Frequently asked questions for 9701 Covalent bonding and coordinate (dative covalent) bonding. Direct answers first, then deeper explanation — then practise with marking.
Once a coordinate bond is formed, is it different from a normal covalent bond?
No. Once formed, a coordinate bond is indistinguishable from any other covalent bond in the molecule or ion. For example, in the ammonium ion (), all four N-H bonds are identical in length and strength. The distinction is only in the 'history' of where the electrons came from.
Can neutral molecules have coordinate bonds?
Yes, absolutely. A common example is the adduct formed between ammonia and boron trifluoride, . The nitrogen donates its lone pair to the electron-deficient boron atom. Another example is carbon monoxide, , which is best represented with a triple bond, one of which is a coordinate bond.
Why is boron in $BF_3$ considered electron deficient?
In boron trifluoride, the central boron atom forms three single covalent bonds with three fluorine atoms. This gives the boron atom only six electrons in its outer shell (3 bonds × 2 electrons/bond = 6 electrons), not a full octet of eight. This makes it 'electron deficient' and able to accept a lone pair from a donor atom.