Question

Consider the first ionization energy of neon and the electron affinity of fluorine. (a) Write equations, including electron configurations, for each process. (b) These two quantities have opposite signs. Which will be positive, and which will be negative? (c) Would you expect the magnitudes of these two quantities to be equal? If not, which one would you expect to be larger?

Short answer

(a) Equations with electron configurations: - Ionization energy of Ne: Ne(\([He]2s^22p^6\)) -> Ne+(\([He]2s^22p^5\)) + e^- - Electron affinity of F: F(\([He]2s^22p^5\)) + e^- -> F-(\([He]2s^22p^6\)) (b) Signs of quantities: - First ionization energy of Ne is positive. - Electron affinity of F is negative. (c) Magnitude comparison: - The first ionization energy of Ne is expected to be larger than the electron affinity of F, due to the larger difficulty in removing an electron from Ne's completely filled and stable 2p orbital compared to adding an electron to F's almost-filled 2p orbital.

Step-by-step solution

(a) Writing Equations with Electron Configurations

For the ionization energy of neon (Ne), we have to remove one electron from a neutral Ne atom, creating a positive ion. The electron configuration of a neutral Ne atom is \([He]2s^22p^6\). Its first ionization energy equation and electron configurations will be: Ne(\([He]2s^22p^6\)) -> Ne+(\([He]2s^22p^5\)) + e^- For the electron affinity of fluorine (F), we need to add an electron to a neutral F atom, creating a negative ion. The electron configuration of a neutral F atom is \([He]2s^22p^5\). Its electron affinity equation and electron configurations will be: F(\([He]2s^22p^5\)) + e^- -> F-(\([He]2s^22p^6\))

(b) Determining the Signs of the Quantities

Ionization energy is the energy needed to remove an electron, and it's always a positive value since the process requires energy input. So, the first ionization energy of neon will be positive. Electron affinity is the energy released when an electron is added to an atom, and it's usually negative since energy is released during the process. The electron affinity value of fluorine will be negative.

(c) Comparison of Magnitudes and Expectations

In general, the magnitudes of ionization energy and electron affinity can be different due to atomic structure and electron-electron repulsion forces. In this case, we're comparing the first ionization energy of neon and electron affinity of fluorine. Neon has a completely filled 2p orbital, making it very stable, and its ionization energy is expected to be high. Fluorine, on the other hand, has almost a completely filled 2p orbital and tends to gain an electron to achieve a stable electron configuration (similar to Ne). Therefore, fluorine has a high electron affinity. However, the first ionization energy of neon is expected to be larger than the electron affinity of fluorine. This is because removing an electron from the completely filled and stable 2p orbital of neon is more difficult compared to adding an electron to the almost-filled 2p orbital of fluorine.

Key concepts

Electron Configuration

Atoms are surrounded by electrons, which are arranged in specific orbitals around the nucleus. These arrangements are known as the electron configuration of an atom. The electron configuration helps to understand an atom's chemical behavior, its reactivity, and its placement in the periodic table.

Neon's electron configuration is particularly interesting as it is considered a noble gas. The configuration for neon (Ne) is \([He]2s^22p^6\). This notation indicates that neon has two electrons in the 2s subshell and six in the 2p subshell. This results in a stable configuration because all its available orbitals in the second shell are completely filled.

In contrast, fluorine (F) has the configuration \([He]2s^22p^5\). Here, you can notice it has one less electron in the 2p subshell compared to neon, which is why it's eager to gain an electron to achieve a stable electron configuration similar to that of neon. By understanding electron configurations, we can predict how and why substances like fluorine are highly reactive while neon remains inert.

Electron Affinity

Electron affinity refers to the amount of energy released when an atom in the gaseous state gains an extra electron. This process often results in the formation of a negative ion. Unlike ionization energy, which requires energy to remove an electron, electron affinity involves the energy change associated with the addition of an electron.

Fluorine is a great example of an element with high electron affinity. Its electron configuration \([He]2s^22p^5\) suggests a strong tendency to gain an electron to fill its 2p subshell completely. When an electron is added to fluorine, creating F\(^-\), its configuration becomes \([He]2s^22p^6\), similar to neon's stable configuration. This process releases energy, and thus fluorine has a negative electron affinity value.

Understanding electron affinity is crucial as it explains why certain elements, like fluorine, are more reactive. Highly negative electron affinities typically mean the element readily accepts electrons, which is why fluorine is one of the most electronegative elements known.

Neon

Neon is a noble gas element, characterized by its complete valence shell, making it extremely stable and chemically inert. The electron configuration of neon \([He]2s^22p^6\) clearly shows that all electrons occupy a full set of orbitals, underlining its stability and lack of reactivity.

Neon's lack of reactivity is mainly due to its full outer shell, making it energetically unfavorable to gain or lose electrons. This is why neon and other noble gases do not easily form chemical compounds or reactions under standard conditions.

When it comes to ionization energy, neon requires a considerable amount of energy to remove one of its electrons. Its high ionization energy is reflective of the strong attraction between its nucleus and the outer electrons. Unlike fluorine, which is eager to gain electrons, neon's stability means it's content staying in its current form, which explains its widespread use in lighting and displays, where it's known for creating bright, colorful lighting when electrically excited.