Question

The compound containing coordinate bond is:
(A) ${{O}_{3}}$
(B) $S{{O}_{3}}$
(C) ${{H}_{2}}S{{O}_{4}}$
(D) All of these

Answer 1

We know that when a pair of electrons are shared by two atoms, a covalent bond is formed. Now when both the electrons shared by the two atoms are of the same atom, the bond formed is a coordinate covalent bond.

Complete step-by-step answer: To determine which of the compounds contain a coordinate bond, we first need to see the Lewis dot structure of all the compounds.
- Ozone (${{O}_{3}}$): Each oxygen atom has 6 electrons in its outermost shell. Since the ozone molecule has 3 oxygen atoms, its Lewis dot structure is as follows:

Here, we can see that the central oxygen atom forms a double bond with one oxygen atom but donates two electrons to the other oxygen atom to form a coordinate bond.
Hence ${{O}_{3}}$ contains a coordinate bond.
- Sulfur Trioxide ($S{{O}_{3}}$): Each oxygen atom has 6 electrons in its outermost shell and each sulfur atom has 6 electrons in its outermost shell. Since each sulfur trioxide molecule has 3 oxygen atoms and 1 sulfur atom, its Lewis dot structure is as follows:

Here, we can see that the central sulfur atom forms double bonds with the oxygen atoms. It has an expanded octet.
Hence $S{{O}_{3}}$ does not contain a coordinate bond.
- Sulfuric Acid (${{H}_{2}}S{{O}_{4}}$): Each oxygen atom has 6 electrons in its outermost shell, each sulfur atom has 6 electrons in its outermost shell and each hydrogen atom has 1 electron in its outermost shell. Since each sulfuric acid molecule has 4 oxygen atoms, 1 sulfur atom, and 2 hydrogen atoms, its Lewis dot structure is as follows:

Here, we can see that the central sulfur atom forms a single bond with 2 oxygen atoms and a double bond with the other 2 oxygen atoms. It has an expanded octet
Hence ${{H}_{2}}S{{O}_{4}}$ does not contain a coordinate bond.

So, the correct answer is option (A) ${{O}_{3}}$ contains a coordinate bond.

Note: This question is tricky as it is easy to assume the presence of coordinate bonds in $S{{O}_{3}}$ and ${{H}_{2}}S{{O}_{4}}$ when one does not know about the phenomenon of expansion of octet.
A non-metal central atom which has empty d-orbitals in its outermost shell and is bonded to highly electronegative atoms may sometimes expand its octet to accommodate more than 8 electrons and form covalent bonds.