asked • 05/10/20

quantum theory and structure

The following values are the only energy levels of a hypothetical one-electron atom:

E6 = -2 x 10-19 J E5 = -7 x 10-19 J E4 = -11 x 10-19 J E3 = -15 x 10-19 J E2 = -17 x 10-19 J E1 = -20 x 10-19 J

(i) If the electron is in the n = 5 level, calculate the highest frequency of radiation that could be emitted.

(ii) Calculate the ionization energy (in kJ mol-1 ) of the atom in its ground state.

(iii) If the electron is in the n = 3 level, calculate the shortest wavelength (in nm) of radiation that could be absorbed without causing ionization. (6 marks)

(d) The ionisation energy generally increases across a period. However, there are two exceptions to the otherwise smooth increase in the first ionisation energy across periods. In Periods 2, there are dips at the Group 3A (13) elements, boron and aluminium, and at the Group 6A (16) elements, oxygen and sulfur. Explain this trend using suitable examples. (7 marks)

1 Expert Answer


Stanton D. answered • 05/11/20

4.6 (42)

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I am still confused for ii).Does it mean that we can take E1 and convert directly without finding any difference in energies


Stanton D.

For the ionization energy, yes. Because that value (a negative amount of energy) IS the amount of energy the electron has, referenced to when it is completely free of the nucleus. So you would have to put that value of energy into it (as a positive number) to bring it to "zero energy" == free of the nucleus, but without any additional kinetic energy. So it is a difference of sorts, between bound in state n=1 and a free electron. By the way, electons can be tickled into very large states (high values of n). The resultant excited atom is called a Rydberg atom, and it can be very large because the electron is so far away from the nucleus!


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