<p>@Benjineering I wasn’t too sure about the acceleration graph. But I’m sure they’d accept any alternate correct procedure for 6b. As for 7c, it asks for the ionization energy for an electron in the ground* state, which the difference between n=1 and n=infinity is 12eV.</p>
<p>And for 7d, electrons can only move to very exact energy levels when they absorb photons with energies that are exactly equal to the difference in energy between the two states. While there is enough energy, it is too much for the n=2 state and too little for the n=3 state, so it won’t leave n=1.</p>
<p>@yayitsme, the difference between n=1 and n=2 is indeed 9eV, but to find the longest wavelength emitted, you must use the smallest energy change which is between n=3 and n=2.</p>