Question

Which of the following molecule has no dative bond?

• A. $CO$
• B. $C{O}_3^{2-}$
• C. $N{H}_4^{+}$
• D. All of these

Answer 1

The correct option is B $C{O}_3^{2-}$

$\left(a\right)$ In the lewis structure of CO, carbon has 4 electrons in its valence shell and oxygen has 6 electrons in its valence shell. So a double bond between carbon and oxygen is formed which leads to completion of octet of $O$ atoms. But $C$ still needs two electrons for its octet completion. Hence, a dative bond is formed between carbon and oxygen. Oxygen donates one of its unshared pair of electrons to carbon so that both carbon and oxygen can have a stable configuration.
$\left(b\right)$

In the Lewis structure of $C{O}_3^{2-},$ $C$ atom in the middle forms 1 double bond with $O$ atom and 2 single bonds with the remaining two oxygen atoms. Since the central $C$ has achieved a stable configaration, the oxygen atoms, even though they have lone pair of electrons they won't be forming a dative bond with the central $C$ atom.

$\left(c\right)$



In case of $N{H}_4^{+}$, nitrogen being a central atom completes its octet by forming covalent bond with 3 hydrogen atom. nitrogen forms a coordinate bond (dative bond) with hydrogen atom and shares his lone pair of electrons.