The electron affinity of each group 5 A element is more...

Name: Problem 106, Chapter 8: Chemistry A Molecular Approach
Uploaded: 2019-07-06T21:03:59-08:00
Duration: 2 min 42 s
Channel: Keenan Mintz
Description: The electron affinity of each group 5 A element is more positive than that of each corresponding group 4 A element. Use the outer electron configurations for these columns to suggest a reason for this observation.

The electron affinity of each group 5 A element is more positive than that of each corresponding group 4 A element. Use the outer electron configurations for these columns to suggest a reason for this observation.

Key Concepts

Electron Pairing and Repulsion

When an extra electron is added to an orbital, it often has to share an orbital with another electron, introducing the effects of electron–electron repulsion and pairing energy. In cases where adding an electron to an element with a half?filled stable configuration forces the electron into a pairing situation (as in group 5A elements), the energy cost from increased repulsion may reduce the overall energetic favorability of the process relative to adding an electron where no repulsion is introduced.

Electron Affinity

Electron affinity refers to the energy change when a neutral atom in the gas phase gains an extra electron to form an anion. It is indicative of how readily an atom accepts an electron. A more positive electron affinity (using a sign?convention where a positive value indicates energy release) implies that the energy released on adding an electron is greater, meaning the process is more favorable.

Outer Electron Configuration

An atom’s outer or valence electron configuration — especially the distribution of electrons in the s and p orbitals — plays a central role in determining its chemical behavior, including electron affinity. In the context of representative elements, the differences in the number of electrons in the p orbitals (for example, having an np2 versus an np3 configuration) determine what changes occur when an extra electron is added.

Half?filled Subshell Stability

Half?filled subshells, such as a p3 configuration, are known to be particularly stable due to symmetry and maximized exchange energy. When an atom already has a half?filled p subshell (as in group 5A elements), it enjoys a special stabilization. Conversely, if adding an electron to a group 4A element results in achieving a half?filled p configuration, this extra stability can make the electron attachment process more exothermic.

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