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Electronegativity and bond polarityEdexcel A-Level Chemistry: Flashcards

What these 13 flashcards ask

  • Define electronegativity.
  • Which element is the most electronegative?
  • How does electronegativity change across a period and down a group?
  • What is a polar bond?
  • Which end of a polar bond carries δ−?
  • Why is Cl–Cl non-polar?
  • Are ionic and covalent bonding completely different?
  • What does a larger electronegativity difference tell you?
  • Why is aluminium chloride more covalent than sodium chloride?
  • Why is CO₂ a non-polar molecule?
  • Why is H₂O a polar molecule?
  • Why is CCl₄ non-polar but CHCl₃ polar?
  • How can you test whether a liquid is polar?

Exam questions on Electronegativity and bond polarity

  1. A chemist compares the hydrogen halides. The Pauling electronegativity values are: H 2.1, F 4.0, Cl 3.0, Br 2.8 and I 2.5.
    Explain why the bond in hydrogen fluoride is polar.2 marks
  2. Some Pauling electronegativity values are: Na 0.9, Mg 1.2, Al 1.5 and Cl 3.0. A student compares the bonding in the chlorides NaCl, MgCl₂ and AlCl₃.
    Explain what is meant by saying that ionic and covalent bonding are the extremes of a continuum, using the bonding in aluminium chloride as an example.2 marks
  3. A teacher brings a charged plastic rod close to a thin stream of liquid running from a burette. The streams of water and trichloromethane, CHCl₃, are deflected towards the rod. The streams of tetrachloromethane, CCl₄, and hexane are not deflected. The Pauling electronegativity values are: H 2.1, C 2.5 and Cl 3.0.
    Explain why tetrachloromethane is not deflected even though it contains polar bonds.3 marks
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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).