Which of the following transitions
is the transition from the ground state to the second excited state of hydrogen?
On the diagram, a horizontal line
indicates an energy level. We can read across the right-hand
side to get the energy of that level. The vertical lines indicate the
transition for an electron from one energy level to another. You may recognize, this question is
using the Bohr model of the atom, where we only have principal quantum numbers, and
we don’t differentiate between types of orbital.
We’re looking for a transition that
starts in the ground state, where the electron is at its most stable. That’s where the energy of the
shell is as low as possible. This is where the electron would be
in the ground state. The energy is as negative, as low
as possible. And we can label this state H. If we promoted the electron from
the 𝑛 equals one shell to the 𝑛 equals two shell, we’d consider the hydrogen atom
in its first excited state and label that with H asterisk.
The question asks us for the
transition from the ground state to the second excited state of hydrogen, which
means we go one step further. If the electron were in the 𝑛
equals three shell, we would consider this, in the Bohr model, the second excited
state. And the transition from the ground
state to the second excited state in this diagram is labeled d.