Arranging Li, Be, B, C, N, O, F, and Ne in Order of Decreasing Electron Affinity

Arranging the elements lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne) in order of decreasing electron affinity requires an understanding of the periodic trends within the periodic table. This involves considering both the general trends across a period and the specific exceptions to these trends, such as neon (Ne) and nitrogen (N).

Electron Affinity Trends

Electron affinity generally follows a specific pattern across the periodic table:

Across a Period

Electron affinity generally increases from left to right across a period due to increasing nuclear charge. As you move from left to right, the nuclear charge increases, pulling in electrons more effectively. This results in a greater tendency to attract an extra electron and thus a higher electron affinity.

Down a Group

Electron affinity generally decreases down a group because the added electron is farther from the nucleus and experiences greater electron-electron repulsion. The further the electron is from the nucleus, the less attractive it is to the positive nucleus, and the more it repels other electrons. This leads to a lower electron affinity as one moves down a group.

Electron Affinities of the Elements

Let's look at the electron affinities for each of the elements listed:

Fluorine (F)

Fluorine has the highest electron affinity, represented by the most negative value. It strongly attracts incoming electrons.

Oxygen (O)

Oxygen has a high electron affinity but is less than fluorine. It tends to attract electrons, but not as strongly as fluorine.

Nitrogen (N)

Nitrogen has a lower electron affinity due to its half-filled p subshell. The stability of a half-filled p subshell makes nitrogen less willing to gain an extra electron.

Boron (B)

Boron's electron affinity is lower than nitrogen’s. Like nitrogen, it has a stable electronic configuration, but it generally has a lower affinity for additional electrons.

Beryllium (Be)

Beryllium has a very low electron affinity and even shows a positive value, indicating a less strong tendency to gain an electron. This is because its configuration is fully stable with only two electrons.

Lithium (Li)

Lithium has a low electron affinity, similar to beryllium but slightly higher. Like other alkali metals, it has a relatively low affinity for additional electrons due to its stable electronic configuration.

Neon (Ne)

Neon has a positive electron affinity, making it unlikely to gain an extra electron. As a noble gas with a full electron configuration, it is very stable and unreactive.

Order of Decreasing Electron Affinity

Based on the trends discussed, the order of the elements from highest to lowest electron affinity is as follows:

Fluorine (F) Oxygen (O) Nitrogen (N) Boron (B) Beryllium (Be) Lithium (Li) Neon (Ne)

This order reflects the decreasing tendency of these elements to gain an extra electron.

Exceptions and Final Arrangement

However, there are some notable exceptions to this general trend:

Neon (Ne) has a full electronic configuration, making it less likely to gain an extra electron. It has the least electron affinity. Nitrogen (N) has a half-filled p subshell, giving it a lower electron affinity than expected due to the stability of the half-filled subshell. Beryllium (Be) also has a full electronic configuration and shows a very low electron affinity. Lithium (Li) has a higher electron affinity than boron (B) due to its desire to achieve a full outer shell, which would make it stable like neon. Boron (B) is lower in electron affinity than nitrogen (N), as it has a full electronic configuration and is thus less likely to gain an extra electron.

Considering these exceptions, the correct order for these elements in decreasing electron affinity is:

Neon (Ne) Nitrogen (N) Beryllium (Be) Boron (B) Lithium (Li) Carbon (C) Oxygen (O) Fluorine (F)

This final arrangement accurately reflects the decreasing tendency of these elements to gain an additional electron.