Question

the photoelectron spectra for h and he are represented above.
which of the following statements best accounts for the fact that the peak on the he spectrum is farther to the left and higher than the peak on the h spectrum?
a he has an additional valence electron in a higher energy level than the valence electron in h.
b he has a greater nuclear charge than h and an additional electron in the same energy level.
c he has a completely filled valence shell in which the electrons are a greater distance from the nucleus than the distance between the h nucleus and its electron.
d it takes longer for the electrons in he to be removed due to the higher nuclear mass of he.

Explanation:

The photoelectron spectrum peak position is related to the energy required to remove electrons. Helium (\(He\)) has a greater nuclear charge (\(+ 2\)) compared to hydrogen (\(H\), \(+1\)). The higher nuclear charge in \(He\) means that the electrons are more strongly attracted to the nucleus. This stronger attraction results in a higher energy required to remove the electrons (as seen by the peak on the \(He\) spectrum being farther to the left and higher in energy). Option B is correct because the greater nuclear charge of \(He\) (compared to \(H\)) causes the electron (in the same energy level, since both \(H\) and \(He\) have electrons in the \(1s\) level) to be more tightly bound.

• Option A is wrong because \(He\) and \(H\) have electrons in the same principal energy level (\(n = 1\)), not \(He\) having a valence electron in a higher - energy level.
• Option C is wrong because electrons in \(He\) are closer to the nucleus (due to higher nuclear charge) compared to \(H\) (not a greater distance).
• Option D is wrong because nuclear mass does not directly affect the ionization energy (electron removal energy) in the way described for photoelectron spectra; it is the nuclear charge (proton number) that mainly affects electron - nucleus attraction.

Answer:

B. He has a greater nuclear charge than H and an additional electron in the same energy level.