Answer:

Explanation:
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In this case, it possible to use the Rydberg equation in order to calculate the wavelength for this transition from n=3 to n=2 as shown below:

Thus, we plug in the corresponding energy levels and the Rydberg constant to obtain:

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The octet rule is that atoms must have 8 valence electrons to have an octet. Usually, when atoms have an octet, they tend not to bond with any other atoms because they are already stable and do not need to bond anymore.