Question about NMR

[I am a unicorn]

Hi everyone

Here's a question that I'm a little confused about:
Order the following molecules from highest to lowest energy required to cause stretching of the bond: HCl, HI, HBr.

The answer is: (starting from highest energy required to cause stretching) HCl, HBr, HI
Why? What determines how much energy is required to cause the bonds to stretch?

Thanks in advance

[IndefatigableLover]

Hi everyone

Here's a question that I'm a little confused about:
Order the following molecules from highest to lowest energy required to cause stretching of the bond: HCl, HI, HBr.

The answer is: (starting from highest energy required to cause stretching) HCl, HBr, HI
Why? What determines how much energy is required to cause the bonds to stretch?

Thanks in advance

Essentially the covalent bonds between HCl, HI and HBr share the same pair of electrons however the distance of the outer electrons to the nucleus of the halogens differ greatly where Chlorine is closer (due to the number of outer shells aka smaller atomic radius compared to HI and HBr). As it has a smaller atomic radius, it is said that the bond is stronger than the others.

As a rule of thumb, the higher mass of the compound under analysis, the lower the energy of radiation is absorbed hence why C-H has a high wavenumber around 3000 in comparison to C-Cl which hovers around 750