Explain the following observations: (1) Helium exhibits more visible emission lines than hydrogen; and (2) the emission wavelengths for helium and hydrogen are different. Please consider the following terms when writing this section: shielding, splitting degeneracies, s-orbital, p-orbital, spin, singlet, triplet, electronic transition.

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.

What is the ima of the 1 st class lever in the graphic given? 2 3 0.5

Can someone me with questions 12 and 13 plz.