Which of these contains only one substance

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.

Provide a stepwise curved arrow mechanism that fully explains the outcome of the reaction shown below. oh нао* heat он

Word equation for k(s) +h2o(l) yield koh (aq) + h2