The table lists bond lengths and bond energies of some hydrogen halides. Hydrogen halide Bond length / nm Bond energy / kJ mol - 1 HCl 0 . 127 431 HBr 0 . 141 366 HI 0 . 161 299 Describe the relationship between the bond length and the bond energy for these hydrogen halides.

Bond length is defined as the average distance between centres of nuclei of two bonded atoms in a molecule. The amount of energy required to break a bond is called bond dissociation energy or bond energy. The important thing about bond length is its relationship with bond energy. For example, in the hydrogen halides, as the bond gets longer, the distance of the electron pair from the nucleus of the halogen atom is going to get much greater, and that weakens the bond. Thus, bond length is increasing from HCl to HI and bond energy is decreasing from HCl to HI . Hence, bond length is inversely proportional to bond energy.

The table lists bond lengths and bond energies of some hydrogen halides. Hydrogen halide Bond length / nm Bond energy / kJ mol - 1 HCl 0 . 127 431 HBr 0 . 141 366 HI 0 . 161 299 Suggest why the bond energy values decrease in the order HCl > HBr > HI .

Bond energy is defined as the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state. Bond energy decreases due to increased bond length with the hydrogen atom. Longer bond length means the bond is easier to break. This happens at the intermolecular level. There is a large difference between electronegativity of two atoms, so the bond is stronger. As we go down the group, the difference between electronegativity decreases and therefore, bond dissociation energy also decreases. Hence, bond energy values decrease in the order HCl > HBr > HI .

The table lists bond lengths and bond energies of some hydrogen halides. Hydrogen halide Bond length / nm Bond energy / kJ mol - 1 HCl 0 . 127 431 HBr 0 . 141 366 HI 0 . 161 299 Suggest a value for the bond length in hydrogen fluoride, HF .

Hydrogen fluoride is formed through covalent bonding between a hydrogen atom and a fluorine atom. Hydrogen contains one electron, and fluorine requires one electron to become stable, so the bond forms readily when the two elements interact. Bond lengths are increasing in hydrogen halides down the group. The bond length of HF is less than the bond length of HCl . Hence, HF bond length is approximately 0 . 091 nm .