Electronegativity and bond polarityAQA A-Level Chemistry: Flashcards

What these 13 flashcards ask

Define electronegativity.
Which element is the most electronegative?
Trend in electronegativity across a period?
Trend in electronegativity down a group?
When is a covalent bond non-polar?
What is a polar covalent bond?
Partial charges in H–Cl?
What is a permanent dipole?
Why does CO₂ have no permanent dipole?
Why is CCl₄ non-polar but CHCl₃ polar?
Why is H₂O polar?
Give three symmetrical molecules with polar bonds and no dipole.
What does a large electronegativity difference lead to?

Exam questions on Electronegativity and bond polarity

Hydrogen chloride, HCl, is a gas that dissolves in water to form hydrochloric acid. The two atoms in an HCl molecule share one pair of electrons, and chlorine is more electronegative than hydrogen.
Explain why the bond in HCl is polar.2 marks
Carbon dioxide, CO₂, and sulfur dioxide, SO₂, both contain polar bonds between oxygen and a central non-metal atom. Oxygen is more electronegative than both carbon and sulfur. A CO₂ molecule is linear, whereas an SO₂ molecule is bent.
Explain why SO₂ has a permanent dipole but CO₂ does not.2 marks
Chlorine is found in several molecules, including chlorine gas, Cl₂, tetrachloromethane, CCl₄, and trichloromethane, CHCl₃. Pauling electronegativity values are 2.5 for carbon, 2.1 for hydrogen and 3.0 for chlorine.
Explain why the bond in Cl₂ is non-polar but the C–Cl bond in CCl₄ is polar, stating the partial charge on each atom in C–Cl.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).