What element has a proton number of 79?

Neils bohr believed that electrons orbited the nucleus in different energy levels, based on strong support from

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?

What is the area in square meters of 448 g ai foil that has a thickness of 23921 nm? the density is 2.70 g/cm