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Elements of Groups 16, 17 and 18 — Chemistry STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElements of Groups 16, 17 and 182 Marks
Question
In case of group 18 elements, explain the variation in melting and boiling points.
✓

Answer

Melting points and boiling points :
  • Group 18 elements have very low melting points and boiling points.
  • The melting points and boiling points increase down the group from He to Rn.
  • As the size of the atoms increases on moving down the group, the magnitude of the van der Waals forces increase from He to Rn.
  • Thus, the melting and boiling points increase from He to Rn. Helium has the lowest boiling point $(4.2 K )$ of any known substance.
  • The boiling points increase in the order He $He < Ne < Ar < Kr < Xe < Rn$

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