Covalent bonding and dative bondsEdexcel International A Level Chemistry: Mind map

Exam questions on Covalent bonding and dative bonds

1. Nitrogen atoms have atomic number 7. In nitrogen gas, N₂, two atoms are joined by a triple bond. X-ray diffraction can be used to produce an electron density map of a molecule such as N₂.
   Explain, in terms of electrostatic forces, how the shared electrons hold the two nitrogen nuclei together.2 marks
2. Ammonia gas reacts with hydrogen chloride gas to form solid ammonium chloride, which contains the ammonium ion, NH₄⁺. In the ammonium ion all four N–H bonds are identical in length and strength. A hydrogen ion, H⁺, has no electrons.
   Explain why all four N–H bonds in the ammonium ion are identical even though one of them is a dative covalent bond.2 marks
3. The vapour of aluminium chloride just above its sublimation temperature has a relative formula mass of 267 (Ar: Al = 27.0, Cl = 35.5). In an AlCl₃ molecule the aluminium atom has only six electrons in its outer shell.
   Deduce the formula of the species in the vapour and explain how it forms from AlCl₃.3 marks