The energy needed to change a He+ ion in the ground state into a He2+ ion is:
A)13.6 eV
B)54.4 eV
C)112.4 eV
D)92.9 eV
E)27.2 eV

Question

Quizplus · Accepted Answer

The energy needed to ionize an electron in a hydrogen atom is 13.6 eV. Since He+ has two electrons, the energy needed to ionize both of them is twice that amount, which is 27.2 eV. However, to convert He+ into He2+ means you need to remove one more electron, which requires an additional 13.6 eV of energy. Therefore, the energy needed to change He+ into He2+ is 27.2 + 13.6 = 40.8 eV. But the question asks for the change in energy, which means we need to take the difference between the energies of He2+ and He+. The energy of He2+ is the sum of the energies of its two remaining protons, which is twice the energy of a hydrogen ion, or 2 x 13.6 eV = 27.2 eV. Therefore, the energy needed to change He+ into He2+ is 27.2 - 13.6 = 13.6 eV x 2 = 27.2 eV. However, the question asks for the actual amount of energy, not the change in energy, so the final answer is B) 54.4 eV.

The Energy Needed to Change a He+ Ion in the Ground