What is actual difference between atomic hydrogen and nascent hydrogen?

1 Answer
Jul 28, 2017

Nascent hydrogen is an old term, outdated even, postulated to describe a "species" of atomic hydrogen gas that was produced in situ (on site), to claim that it is a "highly reactive" version of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)H2(g) stored over a longer period of time.

(Really, it is just an overly-simplified explanation of why such "species" [which are not new to us] tend to be more reactive than bottled ones stored 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)

This is just in general, and out of context of dissolving-metal reactions. I don't think we use the term "nascent hydrogen" anymore...