Neon atom, energy level diagram

We represent each electron with an arrow. Different electron spins m value of -5 or +5) are indicated by arrows pointing downward or upward. Because each line represents one orbital, each line may hold a maximum of two arrows. If two arrows are present, they must be pointing in opposite directions. The energy level diagram representing the neon atom is shown in Figure 4.10. 

Of greater interest in chemistry are lasers in which the active medium is a gas. The most common and least expensive gas laser is the helium-neon laser, which uses a mixture of 85% He and 15% Ne at pressures of the order of 10 torr. An energy-level diagram is shown in Fig. 14.14. An electric discharge excites He atoms to their H 25- S and S states, 19.8and20.6eV above the ground state. This energy... 

These experimental results for neon are consistent with the electron configuration Ne ls 2s 2p predicted by the aufbau principle. Ionization energies measured in this way are used to construct the energy-level diagram for atoms and to show explicitly the value of the ground-state energy. 

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