Chapter 28, Problem 12Q

To determine

Why do the excited hydrogen and excited helium atoms have different emission spectra when they radiate light.

Answer to Problem 12Q

Solution:

The excited hydrogen and excited helium atoms have different emission spectra when they radiate light because the electrons that emit photons do so in very different environments.

Explanation of Solution

In a Hydrogen atom, the electron is under the influence of the force due to one proton. It does not interact with other electrons. This gives characteristic line spectra.

In Helium atoms, there are two electrons and two protons, aside from two neutrons. Thus, any single electron in an excited state would be interacting with another electron of the same orbital but opposite spin, that may or may not be excited itself. Moreover, it is attracted to the forces of two protons. Even in a unipositive Helium atom, the presence of two protons means greater energy transitions. These conditions change the line spectra of Helium atom.