Which of the following transitions
is the transition that represents the ionization of hydrogen?
In the diagram, the horizontal
lines labeled with a number are individual energy levels, while the vertical lines
indicate a possible transition for an electron from one energy level to another. Each energy level is labeled with a
principal quantum number, given the symbol 𝑛. Each number corresponds to a number
of electron shell. The lowest energy level corresponds
to the first electron shell. The question tells us that this
diagram relates to hydrogen. You may have noticed that this
diagram adopts the Bohr model, where there’s no differentiation between types of
orbital in each electron shell. So we have no s, p, d, or f
The most obvious meaning for
ionization is the conversion into an ion. But generally, in chemistry, we
think about ionization as the removal of electrons to form positive ions. This is in contrast to electron
affinities where we’re looking at adding electrons to produce negative ions. An atom of hydrogen consists of a
single electron bound to a nucleus containing only one proton. When discussing ionization of
elements, we assume that their electrons are in their lowest possible energy state,
which means that the atom is in the ground state. This means on the diagram, our
starting point is with the electron in the 𝑛 equals one shell, where the hydrogen
atom is in its ground state.
The ionization of a hydrogen atom
involves the removal of that single electron, forming an H⁺ ion and a free
electron. But in the Bohr model, energy
levels go on forever to the extremes of the universe. So technically, we only class it as
complete ionization when the nucleus of the hydrogen atom and the electron from the
hydrogen atom are infinitely separated. This hypothetical state is given
the principal quantum number ∞. So this is the energy level where
our transition must end, where 𝑛 equals ∞.
The transition of the five that
starts at the ground state and finishes at 𝑛 equals ∞ is this one, c.