How can we guess whether a compound has a co-ordinate bond or not?For example in case of ozone we can also make the structure without co-ordinate bond but it surely has co-ordinate bond.Please help meI will surely approve all correct answers.

Dear student,

In simple diagrams, a co-ordinate bond is shown by an arrow. The arrow points from the atom donating the lone pair to the atom accepting it.

Dissolving hydrogen chloride in water to make hydrochloric acid

Something similar happens. A hydrogen ion (H⁺) is transferred from the chlorine to one of the lone pairs on the oxygen atom.

The H₃O⁺ ion is variously called the hydroxonium ion, the hydronium ion or the oxonium ion.

In an introductory chemistry course (such as GCSE), whenever you have talked about hydrogen ions (for example in acids), you have actually been talking about the hydroxonium ion. A raw hydrogen ion is simply a proton, and is far too reactive to exist on its own in a test tube.

If you write the hydrogen ion as H⁺_(aq), the "_(aq)" represents the water molecule that the hydrogen ion is attached to. When it reacts with something (an alkali, for example), the hydrogen ion simply becomes detached from the water molecule again.

Note that once the co-ordinate bond has been set up, all the hydrogens attached to the oxygen are exactly equivalent. When a hydrogen ion breaks away again, it could be any of the three.