"nd" is nitrogen dioxide?
That's how kids these days spell the word and when they are texting to their girlfriends. Kids who are doomed to fail in school often get confused and think it should be spelled that way all the time. Even when trying to get help from educated people. That usually leads to their demise and eventual flunk out. It gets really entertaining when they use that sort of stuff in class assignments then get mad when the whole thing gets marked with a zero and a note that I will not waste my time tryingto read it.