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Ch.7 - Periodic Properties of the Elements
Chapter 7, Problem 6d

Shown below is a qualitative diagram of the atomic orbital energies for an Na atom. The number of orbitals in each subshell is not shown.
Diagram showing atomic orbital energies for a sodium atom, illustrating energy levels 3s and 3p.
(d) A sodium vapor lamp (Figure 7.23) operates by using electricity to excite the highest-energy electron to the next highest-energy level. Light is produced when the excited electron drops back to the lower level. Which two energy levels are involved in this process for the Na atom?

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1
Identify the highest-energy electron in the Na atom. For sodium (Na), the electron configuration is 1s^2 2s^2 2p^6 3s^1. The highest-energy electron is in the 3s orbital.
Determine the next highest-energy level. From the diagram, the next highest-energy level after 3s is the 3p orbital.
Understand the excitation process. In a sodium vapor lamp, electricity excites the highest-energy electron from the 3s orbital to the 3p orbital.
Recognize the light emission process. Light is produced when the excited electron drops back from the 3p orbital to the 3s orbital.
Conclude the energy levels involved. The two energy levels involved in this process for the Na atom are the 3s and 3p orbitals.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Orbitals

Atomic orbitals are regions around an atom's nucleus where electrons are likely to be found. Each orbital has a specific energy level and shape, categorized into subshells such as s, p, d, and f. In the case of sodium (Na), the 3s and 3p orbitals are relevant, as they represent the highest energy levels occupied by electrons in the ground state.
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Electron Excitation

Electron excitation occurs when an electron absorbs energy and moves from a lower energy level to a higher one. In sodium vapor lamps, electricity provides the energy needed to excite the highest-energy electron from the 3s orbital to the 3p orbital. This process is crucial for the production of light, as the electron will eventually return to a lower energy state, releasing energy in the form of light.
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Energy Level Transitions

Energy level transitions refer to the movement of electrons between different energy states within an atom. For sodium, the transition from the 3s to the 3p level is significant when discussing the emission of light. When the excited electron falls back to the 3s level, it releases energy as a photon, which is the light observed in sodium vapor lamps.
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