What is actual difference between atomic hydrogen and nascent hydrogen?

Question

Avery Adams · Accepted Answer

Nascent hydrogen is an old term, outdated even, postulated to describe a "species" of atomic hydrogen gas that was produced in situ (on site), to claim that it is a "highly reactive" version of #"H"_2(g)# stored over a longer period of time.

(In actuality, it is merely an oversimplified explanation for why these "species"—which are not particularly new to us—tend to be more reactive than ones that have been preserved in bottles over time.)

#"Zn"(s) + "H"_2"SO"_4(aq) -> "ZnSO"_4(aq) + overbrace(2"H"(g))^"'Nascent Hydrogen'"#

This tends to be in the context of dissolving-metal reactions. Although I usually see this reaction forming #"H"_2(g)#, this process shown above is at around #4000 - 4500^@ "C"#, which promotes homolytic cleavage of #"H"_2# into #2"H"#.

(These days, we know that of course it's more reactive than #"H"_2(g)#... #"H"cdot# is a radical!)

Atomic hydrogen is more generalized, and is simply the #"H"# atom, one proton plus one electron.

#"H"_2(g) + "436 kJ" -> 2"H"(g)#

I think the term "nascent hydrogen" is no longer used; this is just general information taken out of the context of dissolving-metal reactions.

Xavier Avery · Answer

undefined While nascent hydrogen is defined as hydrogen atoms that are highly reactive and usually produced in situ during a chemical reaction, atomic hydrogen is defined as a hydrogen atom in its ground state, which consists of a single proton and one electron. Nascent hydrogen is often produced in the form of hydrogen radicals (H•) or hydrogen atoms with unpaired electrons, which make them highly reactive and capable of participating in various chemical reactions.