The following molecules have double covalent bonds between two atoms except?

Analyze the question: We need the molecule that does NOT contain a double covalent bond between two atoms.

Concept: A double covalent bond means two atoms share two pairs of electrons (shown as =).

Checking each option:

• A. Oxygen (O₂): O=O. Each oxygen atom needs 2 more electrons, so they share two pairs. This is a double bond.
• B. Carbon (IV) oxide (CO₂): O=C=O. Carbon forms a double bond with each oxygen atom. This has double bonds.
• C. Ethene (C₂H₄): H₂C=CH₂. There is a C=C double bond. This has a double bond.
• D. Water (H₂O): H–O–H. Oxygen shares one pair of electrons with each hydrogen atom, and hydrogen needs only one electron to fill its shell (duplet). So only single bonds exist, plus two lone pairs on oxygen.

Answer: Water is the only molecule with no double bond, so the correct option is D.

Tip: Hydrogen can only ever form a single bond because it needs just one more electron to complete its duplet. So any molecule where the bonds are all to hydrogen (like H₂O, NH₃, CH₄) will have only single bonds. Remember: O₂ is double-bonded, N₂ is triple-bonded, and CO₂ has two double bonds.