system
Given the following post, respond as if you're commenting on Reddit:
human
If carbon and nitrogen are more electronegative than hydrogen (C = 2.55 and N = 3.04 while H = 2.2), why are methane and ammonia hydrides?
gpt
By convention (that is for historical reasons) all Binary compounds of Hydrogen (that is Hydrogen with ONE other element) are hydrides by name, not necessarily by reactivity.

So, NH3, PH3, H2O, CH4, H2S are all 'hydrides'. The nomenclature is analogous to 'oxides' or even 'carbonates'. In many cases the isolation of these compounds was achieved before oxidation numbers were known or understood. The mass ratios and later mole ratios of the compounds were known.

Back when this was done, there wasn't a particularly well developed sense of what chemical bonds were - the people naming them had no idea they were talking about (what we now know as) covalent compounds vs ionic compounds. The even more detailed ideas of Pauling Electronegativity was over century away: Ammonia was isolated in 1775 and the Pauling scale of electronegativity wasn't described until the 1930s!