Which of the following does not contain any co-ordinate bond?
A. H3O+

B. BF4−

C. HF2−

D. NH4+

To solve this, let's first understand what a coordinate bond (also called a dative covalent bond) is. A coordinate bond is formed when one atom provides both electrons for a shared pair in a covalent bond.

Now, let's analyze each option:

A. H₃O⁺ (Hydronium ion):
In this ion, the oxygen atom forms three normal covalent bonds with three hydrogen atoms. Additionally, the oxygen atom donates a lone pair to bond with an extra proton (H⁺), forming a coordinate bond.
Contains a coordinate bond.
B. BF₄⁻ (Tetrafluoroborate ion):
Boron has three valence electrons and forms three normal covalent bonds with fluorine. However, in BF₄⁻, boron accepts an extra lone pair from one of the fluorine atoms to form a fourth bond, making it a coordinate bond.
Contains a coordinate bond.
C. HF₂⁻ (Bifluoride ion):
In HF₂⁻, a hydrogen atom is bonded to two fluoride ions. One of the fluoride ions forms a normal covalent bond with hydrogen, while the other fluoride shares its lone pair with hydrogen, creating a coordinate bond.
Contains a coordinate bond.
D. NH₄⁺ (Ammonium ion):
In NH₄⁺, nitrogen has five valence electrons. It forms three covalent bonds with three hydrogen atoms and donates its lone pair to bond with an additional hydrogen ion (H⁺), but this lone pair is used up in making the ion positive.
Does not contain a coordinate bond, as all bonds are normal covalent bonds.
Conclusion:
The correct answer is D. NH₄⁺, as it does not contain any coordinate bonds.