Shapes of molecules and ionsEdexcel A-Level Chemistry: Flashcards
What these 13 flashcards ask
- What decides the shape of a molecule?
- What is the shape and angle with 2 bonding pairs and no lone pairs?
- What is the shape and angle of BCl₃?
- What is the shape and angle of CH₄ and NH₄⁺?
- What is the shape and bond angle of NH₃?
- What is the shape and bond angle of H₂O?
- What is the order of electron pair repulsion?
- Why is the angle in H₂O smaller than in NH₃?
- What is the shape of PCl₅ and its bond angles?
- What is the shape and bond angle of SF₆?
- How do you work out the number of lone pairs?
- What is the shape of XeF₄ and why?
- Does a double bond count as one region of repulsion?
Exam questions on Shapes of molecules and ions
- Boron trichloride, BCl₃, is a gas used in the manufacture of semiconductors. It reacts with ammonia, NH₃, to form a solid adduct, H₃N→BCl₃, in which the boron atom is bonded to four atoms.Explain why the Cl–B–Cl bond angle changes from 120° in BCl₃ to about 109.5° in the adduct.2 marks
- The H–X–H bond angles in three hydrides of second-row elements are measured as 109.5° in methane, CH₄, 107° in ammonia, NH₃, and 104.5° in water, H₂O.Explain why the bond angle in water is smaller than the bond angle in ammonia.2 marks
- Sulfur hexafluoride, SF₆, is an unreactive gas used to insulate electrical switchgear. Phosphorus pentachloride, PCl₅, is a reagent used in organic chemistry. Both are simple molecules in the gas phase. Phosphorus has five outer electrons, sulfur has six and bromine has seven.Deduce the shape of a gaseous PCl₅ molecule and the bond angles in it, explaining your answer.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).