What is TRUE about elements in the SAME row/period on the periodic table (select ALL that apply) PLEASE HEL

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.

Which of these conditions most likely produces an unstable isotope?

Is a pencil falling to the floor anon contact force, a force, or a contact force