Which elements were decribed as the transition element by mendeleev.

1. N

2.Ni

3.Ne

4.None

I think its Ni but i think there were no transition element in mendeleev's periodic table please help me
i will mark you as branliest
plz help.

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?