Question

Explain the formation of H₃O⁺ and NH₄⁺ ion. 

Answer 1

Formation of Hydronium ion, H₃O⁺ : This ion formed by the combination of H₂O molecule and H⁺ ion. The water molecule has two O—H covalent bonds and central oxygen atom has two lone pairs of electrons. H+ ion has one vacant ls-orbital. During the formation of H₃O⁺ , one pair of lone pair from O-atom is donated to the vacant ls-orbital of H⁺ ion and O — H co-ordinate bond is formed. Thus H₃O⁺ ion contains two O—H covalent bonds and one O— H co-ordinate bond. After the formation O→ H⁺ co-ordinate bond becomes identical to the two O—H covalent bonds. Hence in H₃O + ion all the three bonds are identical.

Formation of NH₄⁺ , Ammonium ion : This ion formed by the combination of NH₃ molecule and H⁺ ion. In NH₃ molecule each of three H^-atoms is linked to N-atom by a covalent bond. Thus in this molecule N-atom is left with a lone pair of electrons after completing its. octet by sharing three of its valence shell electrons with three H-atoms. The electrons of lone pair on N-atom are donated to H⁺ ion and thus a N/EH co-ordinate bond is established in NH₄⁺ ion.