Explain7 marksChallenge
Fluorine reacts with hydrogen even in the dark at room temperature, whereas chlorine requires light or a flame, and iodine only reacts slowly when heated. The hydrogen halides formed decompose on heating, and their ease of decomposition decreases from hydrogen iodide to hydrogen fluoride.
Explain, in terms of the electronic structures of the halogen atoms, the trend in reactivity of the halogens with hydrogen from fluorine to iodine, and explain the trend in thermal stability of the hydrogen halides in terms of bond strengths.