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Continuation of Why do nitrogen-containing organic compounds give N2 as the combustion product? (comment converted into question)

Nascent state is an obsolete theory in chemistry and is discredited. However, nascent nitrogen is still relevant in metallurgical domain especially in the "nitriding process". Basically, nitriding is a process of diffusing nascent nitrogen into the surface of steel, iron and other metals like chromium, aluminum etc. (since ordinary nitrogen is inert at treatment temperatures in the range of 500-600 °C). Ammonia acts as a source of nascent nitrogen because at treatment temperature, it dissociates into nitrogen and hydrogen which cracks on the metal surface and then diffuses into the metal to form respective metal nitrides which creates high hardness in the surface of the nitrided component. This nitrided layer is called the "white layer".

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Question: Why is the term nascent nitrogen still used although the theory has become obsolete? Isn't atomic nitrogen a better term?

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    $\begingroup$ Most likely because of their long history of using it with a specific metallurgical meaning which, while based on the old chemistry notion, has acquired a life of its own. They don't flow 'atomic nitrogen' into the ovens, the flow ammonia that ultimately gives the nitrogen. And, details of the exact process occurring on the surface are of passing importance as long as it happens fast enough. So, I'd say that the metallurgical term is distinct from, albeit originally based on, the old chemistry term. $\endgroup$
    – Jon Custer
    Aug 4, 2021 at 12:38
  • $\begingroup$ I doubt there's actual atomic nitrogen in any reaction, that isn't conducted under extreme conditions. $\endgroup$
    – Mithoron
    Aug 4, 2021 at 12:50
  • $\begingroup$ I do not remember ever using the term "nascent nitrogen" altough I have dealt with nitrided steels and nitrogen in titanium. The "whitelayer" of nitrided steels is generally undefined composition, poorly understood. And considered the use of N as an alloy element adding pitting resistance to stainless type steels. $\endgroup$
    – blacksmith37
    Aug 4, 2021 at 16:10
  • $\begingroup$ Nilay Ghosh, I removed the ridicule wording from that Wikipedia essay because none of the two articles ridiculed the nascent hydrogen theory but rather showed that there is no need to invoke a species may not exist. $\endgroup$
    – AChem
    Aug 4, 2021 at 20:25
  • $\begingroup$ The simple answer is probably that metallurgists are not chemists and stick with imprecise terminology that no chemist thinks means anything because, in the context of metallurgy, they it means something specific and the actual chemistry behind it isn't relevant. $\endgroup$
    – matt_black
    Aug 5, 2021 at 17:00

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As we discussed in the previous query Is there any evidence, any evidence at all, that nascent hydrogen actually exists?, the nascent terminology is still in use even in good ACS / RSC journals, which are pretty selective. However, science does not rest on authority; seeing the usage of nascent (gas) does not make it an absolute truth whoever is the author. This type of wording can creep in ocassionally. The idea of nascent hydrogen, oxygen, chlorine, nitrogen was not discredited recently, and people have been arguing against or in favor of it for a long time.

I think in modern terminology, the word nascent is simply a placeholder term when the reaction mechanism is precisely not known or clear. Sometimes, it was unnecessary to invoke a nascent "gas" (esp. hydrogen) in some clear-cut cases. For example, borohydride reduces arsenic ions to arsine-this method is used in very sensitive analytical procedures, and people thought it was nascent hydrogen making this reduction. Not so.

One intriguing example is that if an electric discharge is passed through pure nitrogen, it remains pretty reactive for a while! It ignites in contact with iodine or sulfur, whereas ordinary nitrogen does not even bother to react with them. See Bakerian Lecture on Chemically Active Form of Nitrogen.

Now one cannot replace nascent nitrogen with atomic nitrogen because nascent nitrogen does not need to be in a single atomic state. It could be an excited nitrogen molecule or a singly ionized atom or could be a nitrogen radical. Who knows? I only see people putting forward hypothesis without any convincing experiments. Unless there is a proof, people will continue to use dummy placeholder as nascent nitrogen. Atomic nitrogen would be too restrictive-hence the placeholder term "nascent nitrogen" in metallurgy too.

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