Question

The conversion of atomic hydrogen into ordinary hydrogen is:

• A. exothermic change
• B. endothermic change
• C. nuclear change
• D. photochemical change

Answer 1

The correct option is A exothermic change

The conversion of atomic hydrogen into an ordinary hydrgen is an exothermic reaction. Atomic hydrogens have excess energy and are highly unstable so when they combine to form a stable $H_2$ molecule of low energy, it will release the excess energy in the form of heat. Hence it a exothermic reaction.
Exothermic reactions are reactions that release energy, usually in the form of heat or light.
$2H\to H_2;\Delta H=104.5kcal$