CAIE A Level Chemistry 9701 · Chemical bonding
Ammonia gas reacts with hydrogen chloride gas to form solid ammonium chloride. The ammonium ion, , contains a coordinate (dative covalent) bond. Explain, in terms of electrons and orbitals, how this coordinate bond is formed, and why all four bonds in the ammonium ion are identical.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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