Home · A-Level Chemistry 9701 · Group 17 · Physical properties of the halogens · Practice
AS · Practice questions · Physical properties of the halogens

Down the column.

Six original Cambridge-style questions on the physical properties of the halogens.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Forces between molecules versus the bond inside.

01
Recall
[3 marks]

Give the colour and physical state at room temperature of chlorine, bromine and iodine.

  • Chlorine: pale yellow-green gas. ✓
  • Bromine: red-brown liquid. ✓
  • Iodine: grey-black solid (purple vapour). ✓
02
Explain
[3 marks]

Explain the trend in volatility from chlorine to iodine.

  • Volatility decreases down the group. ✓
  • The molecules have more electrons, so the instantaneous dipole-induced dipole forces between them are stronger. ✓
  • More energy is needed to separate the molecules, so the boiling point is higher. ✓
03
Explain
[2 marks]

Explain why the bond energy decreases from Cl–Cl to I–I.

  • The atoms get larger, so the bond is longer. ✓
  • The bonding pair is further from the nuclei and more shielded, so it is attracted less strongly. ✓
04
Explain
[2 marks]

Suggest why the F–F bond energy (158 kJ mol−1) is lower than that of Cl–Cl (242 kJ mol−1).

  • Fluorine atoms are very small, so the F–F bond is very short. ✓
  • The lone pairs on the two atoms are close together and repel, weakening the bond. ✓
05
Analysis
[2 marks]

Predict the state and colour of astatine at room temperature and give a reason.

  • A black solid. ✓
  • Colours darken and boiling points rise down the group; astatine has even more electrons than iodine. ✓
06
Explain
[2 marks]

When iodine crystals are warmed gently, a purple vapour forms. State whether any covalent bonds are broken and explain.

  • No covalent bonds are broken. ✓
  • Only the weak id-id forces between I2 molecules are overcome; the vapour is still I2. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.