Question:

The variation of the boiling points of the hydrogen halides is in the order $HF > HI > HBr > HCl$. What explains the higher boiling point of hydrogen fluoride ?

Updated On: Jul 13, 2024
  • The bond energy of HF molecules is greater than in other hydrogen halides
  • The effect of nuclear shielding is much reduced in fluorine which polarises the HF molecule
  • The electronegativity of fluorine is much higher than for other elements in the group.
  • There is strong hydrogen bonding between HF molecules
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The Correct Option is D

Solution and Explanation

Due to strong H-bonding in HF molecule, boiling point is highest for HF
HF > HI > HBr > HI
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Concepts Used:

Group 17 Elements

Halogens are the group 17 elements of the periodic table. The term ‘halogen’ means ‘salt-producing’, hence the name halogens as they possess the tendency to form salts after reacting to metals. It generally has five elements:

  • Fluorine (F)
  • Chlorine (Cl)
  • Bromine (Br)
  • Iodine (I)
  • Astatine (At)

These are all naturally occurring halogens but Tennessine (Ts) is an artificially created halogen.

Halogens:

Halogens are highly reactive elements and are highly electronegative. They have a high tendency to react with metals to form salts. They are also known as Group 17 elements. They have 7 electrons in their outer shell with a configuration of (ns2 np5). Fluorine being the first halogen in group 17, is highly reactive. Astatine is a halogen because of its resemblance with iodine despite it being radioactive.

Electronic Configuration:

The general electronic configuration for group 17 elements is ns2np5. This configuration clearly shows that they have 7 electrons in their valence shell. They require one more electron to complete their octet and achieve noble gas configuration.