The bond formed between H2O and H+ to form the hydroxonium H3O+ is

Step 1: Analyze the question The question asks what type of bond forms when a water molecule (H₂O) combines with a hydrogen ion (H⁺) to give the hydroxonium ion (H₃O⁺).

Step 2: Explain the concept

• Covalent bond: each atom contributes one electron to the shared pair.
• Dative (coordinate covalent) bond: one atom supplies both electrons of the shared pair, and the other atom supplies none.
• Ionic (electrovalent) bond: electrons are transferred from one atom to another, and the oppositely charged ions attract each other.

Step 3: Work through the solution

• Oxygen in H₂O has two bond pairs and two lone pairs of electrons.
• The H⁺ ion has no electrons (it has lost its only electron), so it has an empty 1s orbital.
• Oxygen donates one of its lone pairs into the empty orbital of H⁺, and the two atoms share that pair.

H₂O: + H⁺ → [H₂O→H]⁺ = H₃O⁺

Since both electrons in the new O–H bond come from the oxygen atom, this is a dative (coordinate) bond.

Note that "covalent" (B) is not the best answer. A dative bond is technically a type of covalent bond, but the question asks for the specific bond type, and what makes this one special is that the electron pair comes from one atom only. Once formed, the bond is indistinguishable from the other O–H bonds in H₃O⁺. Ionic and electrovalent (C and D) are wrong because no electron transfer occurs; the electrons are shared.

Step 4: Answer The correct option is A. Dative.

Exam tip: Remember "lone pair + empty orbital = dative bond". The same idea explains the formation of NH₄⁺ (from NH₃ + H⁺) and the bonding in complex ions. Whenever you see H⁺ joining a molecule, think dative.