How does atomic hydrogen react differently from molecular hydrogen?

Atomic hydrogen and molecular hydrogen differ significantly in their chemical reactivity, primarily due to the high energy required to break the bond in the hydrogen molecule ($H_2$).1

Molecular Hydrogen

Molecular hydrogen is relatively inert at room temperature because of its high dissociation energy (104 kcal/mole). While it can react with many elements and compounds, these reactions typically require elevated temperatures, catalysts, or specific conditions like sparks or radiation to proceed at measurable rates.1

Atomic Hydrogen

Atomic hydrogen is highly reactive and is generated by supplying sufficient energy to dissociate $H_2$ molecules, such as through an electric discharge or contact with a white-hot filament. Its distinct chemical behaviors include:1
* Hydride Formation: It readily combines with most elements to form hydrides, such as sodium hydride (NaH).1
* Reduction: It acts as a powerful reducing agent, capable of reducing metallic oxides to their elemental metallic state.1
* Recombination: In the presence of certain metal surfaces (e.g., platinum) that do not form stable hydrides, atomic hydrogen atoms recombine to form $H_2$ molecules, releasing significant energy that can heat the metal to incandescence.1