Peak 1: 46.72 × 10^3 kJ/mol (relative height 2) Peak 2: 3.88 × 10^3 kJ/mol (relative height 2) Peak — Atomic Structure Chemistry Question
Problem Context
Peak 1: 46.72 × 10^3 kJ/mol (relative height 2)
Peak 2: 3.88 × 10^3 kJ/mol (relative height 2)
Peak 3: 1.68 × 10^3 kJ/mol (relative height 3)
[VISUAL]
The complete photoelectron spectrum of an unknown element is shown above. The frequency ranges of different regions of the electromagnetic spectrum are given in the table below.
| Region of Electromagnetic Spectrum | Frequency Range (s^−1) |
| --- | --- |
| Infrared (IR) | 1 × 10^12 to 4 × 10^14 |
| Ultraviolet/visible (UV/vis) | 4 × 10^14 to 5 × 10^16 |
| X-rays | 5 × 10^16 to 1 × 10^19 |
| Gamma rays | > 1 × 10^19 |
Model Answer
Calculates the energy of a single photon:
E = (7 × 10^4 kJ/mol) / (6.022 × 10^23 photons/mol) = 1.16 × 10^−19 kJ = 1.16 × 10^−16 J
Calculates the frequency of the photon:
ν = E/h = (1.16 × 10^−16 J) / (6.626 × 10^−34 J s) = 1.75 × 10^17 s^−1
Identifies the region:
The radiation is in the X-ray region because the calculated frequency of 1.75 × 10^17 s^−1 falls within the range of 5 × 10^16 to 1 × 10^19 s^−1.
Scoring Guidelines:
- 1 point is earned for calculating the amount of energy per photon.
- 1 point is earned for the frequency and region of the spectrum.
Model Answer
(i) The subshell from which an electron is removed in the second ionization of an atom of the element:
2p
1 point is earned for the correct answer.
(ii) The subshell that corresponds to the second peak of the photoelectron spectrum above:
2s
1 point is earned for the correct answer.